Systems and methods for low-overhead wireless beacons having next full beacon indications

ABSTRACT

Systems, methods, and devices for communicating a compressed beacon are described herein. In some aspects, a method of communicating in a wireless network. includes generating a compressed beacon. The compressed beacon includes a next full beacon time indication (NFBTI). The method further includes transmitting, at an access point, the compressed beacon.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.51/506,136, filed Jul. 10, 2011; U.S. Provisional Application No.51/531,522, filed Sep. 5, 2011; U.S. Provisional Application No.51/549,638, filed Oct. 20, 2011; U.S. Provisional Application No.51/568,075, filed Dec. 7, 2011; U.S. Provisional Application No.51/578,027, filed Dec. 20, 2011; U.S. Provisional Application No.51/583,890, filed Jan. 5, 2012; U.S. Provisional Application No.51/584,174, filed Jan. 5, 2012; U.S. Provisional Application No.51/585,044, filed Jan. 10, 2012; U.S. Provisional Application No.51/596,106, filed Feb. 7, 2012; U.S. Provisional Application No.51/596,775, filed Feb. 9, 2012; U.S. Provisional Application No.51/606,175, filed Mar. 2, 2012; U.S. Provisional Application No.51/618,966, filed Apr. 2, 2012; and U.S. Provisional Application No.51/620,869, filed Apr. 5, 2012, all of which are hereby incorporatedherein by reference, in their entirety. This application is related toU.S. application Ser. No. ______ (Attorney Docket No. 112733U1), titled“SYSTEMS AND METHODS FOR LOW-OVERHEAD WIRELESS BEACONS HAVING COMPRESSEDNETWORK IDENTIFIERS,” filed on even date herewith, and U.S. applicationSer. No. ______ (Attorney Docket No. 112733U3), titled “SYSTEMS ANDMETHODS FOR LOW-OVERHEAD WIRELESS BEACON TIMING,” filed on even dateherewith, both of which are hereby incorporated herein by reference, intheir entirety.

BACKGROUND

1. Field

The present application relates generally to wireless communications,and more specifically to systems, methods, and devices for compressingwireless beacons.

2. Background

In many telecommunication systems, communications networks are used toexchange messages among several interacting spatially-separated devices.Networks may be classified according to geographic scope, which couldbe, for example, a metropolitan area, a local area, or a personal area.Such networks would be designated respectively as a wide area network(WAN), metropolitan area network (MAN), local area network (LAN),wireless local area network (WLAN), or personal area network (PAN).Networks also differ according to the switching/routing technique usedto interconnect the various network nodes and devices (e.g. circuitswitching vs. packet switching), the type of physical media employed fortransmission (e.g. wired vs. wireless), and the set of communicationprotocols used (e.g. Internet protocol suite, SONET (Synchronous OpticalNetworking), Ethernet, etc.).

Wireless networks are often preferred when the network elements aremobile and thus have dynamic connectivity needs, or if the networkarchitecture is formed in an ad hoc, rather than fixed, topology.Wireless networks employ intangible physical media in an unguidedpropagation mode using electromagnetic waves in the radio, microwave,infra-red, optical, etc. frequency bands. Wireless networksadvantageously facilitate user mobility and rapid field deployment whencompared to fixed wired networks.

The devices in a wireless network may transmit/receive informationbetween each other. The information may include packets, which in someaspects may be referred to as data units or data frames. The packets mayinclude overhead information (e.g., header information, packetproperties, etc.) that helps in routing the packet through the network,identifying the data in the packet, processing the packet, etc., as wellas data, for example user data, multimedia content, etc. as might becarried in a payload of the packet.

Access points may also broadcast a beacon signal to other nodes to helpthe nodes synchronize timing or to provide other information orfunctionality. Beacons may therefore convey a large amount of data, onlysome of which may be used by a given node. Accordingly, transmission ofdata in such beacons may be inefficient due to the fact that much of thebandwidth for transmitting beacons may be used to transmit data thatwill not be used. Thus, improved systems, methods, and devices forcommunicating packets are desired.

SUMMARY

The systems, methods, and devices of the invention each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this invention as expressed bythe claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this invention provide advantages that include decreasingthe size of a wireless beacon frame, thereby reducing the overhead intransmitting beacon signals.

One aspect of the disclosure provides a method of communicating in awireless network. The method includes generating a compressed beacon.The compressed beacon includes a next full beacon time indication(NFBTI). The method further includes transmitting, at an access point,the compressed beacon.

Another aspect of the invention provides a method of communicating in awireless network. The method includes receiving, at a wireless device, acompressed beacon including a next full beacon time indication (NFBTI).The method further includes operating the wireless device in a firstpower mode for a duration based on the next full beacon time indication.The method further includes transitioning the wireless device to asecond power mode at the end of the duration. The wireless deviceconsumes a first power when in the first power mode, and a second powerwhen in the second power mode. The first power is lower than the secondpower.

Another aspect of the invention provides wireless device configured tocommunicate in a wireless network. The wireless device includes aprocessor configured to generate a compressed beacon. The compressedbeacon includes a next full beacon time indication (NFBTI). The wirelessdevice further includes a transmitter configured to transmit thecompressed beacon.

Another aspect of the invention provides wireless device configured tocommunicate in a wireless network. The wireless device includes areceiver configured to receive a compressed beacon. The compressedbeacon includes a next full beacon time indication (NFBTI). The wirelessdevice further includes a processor configured to operate the wirelessdevice in a first power mode for a duration based on the next fullbeacon time indication. The processor is further configured totransition the wireless device to a second power mode at the end of theduration. The wireless device consumes a first power when in the firstpower mode, and a second power when in the second power mode. The firstpower is lower than the second power.

Another aspect of the invention provides an apparatus for communicatingin a wireless network. The apparatus includes means for generating acompressed beacon. The compressed beacon includes a next full beacontime indication (NFBTI). The apparatus further includes means fortransmitting the compressed beacon.

Another aspect of the invention provides an apparatus for communicatingin a wireless network. The apparatus includes means for receiving acompressed beacon. The compressed beacon includes a next full beacontime indication (NFBTI). The apparatus further includes means foroperating a wireless device in a first power mode for a duration basedon the next full beacon time indication. The apparatus further includesmeans for transitioning the wireless device to a second power mode atthe end of the duration. The wireless device consumes a first power whenin the first power mode, and a second power when in the second powermode. The first power is lower than the second power.

Another aspect of the invention provides a non-transitorycomputer-readable medium including code that, when executed, causes anapparatus to generate a compressed beacon. The compressed beaconincludes a next full beacon time indication (NFBTI). The medium furtherincludes code that, when executed, causes the apparatus to transmit thecompressed beacon.

Another aspect of the invention provides a non-transitorycomputer-readable medium including code that, when executed, causes anapparatus to receive a compressed beacon. The compressed beacon includesa next full beacon time indication (NFBTI). The medium further includescode that, when executed, causes the apparatus to operate a wirelessdevice in a first power mode for a duration based on the next fullbeacon time indication. The medium further includes code that, whenexecuted, causes the apparatus to transition the wireless device to asecond power mode at the end of the duration. The wireless deviceconsumes a first power when in the first power mode, and a second powerwhen in the second power mode. The first power is lower than the secondpower.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a wireless communication system inwhich aspects of the present disclosure may be employed.

FIG. 2 illustrates various components, including a receiver, that may beutilized in a wireless device that may be employed within the wirelesscommunication system of FIG. 1.

FIG. 3 illustrates an example of a beacon frame used in legacy systemsfor communication.

FIG. 4 illustrates an example low-overhead beacon frame.

FIG. 5 illustrates another example low-overhead beacon frame.

FIG. 6 is a timing diagram illustrating exemplary beacon timing.

FIG. 7 shows a flowchart of an exemplary method for generating acompressed, or low-overhead, beacon.

FIG. 8 is a functional block diagram of an exemplary wireless devicethat may be employed within the wireless communication system of FIG. 1.

FIG. 9 shows a flowchart of an exemplary method for processing acompressed, or low-overhead, beacon.

FIG. 10 is a functional block diagram of another exemplary wirelessdevice that may be employed within the wireless communication system ofFIG. 1.

FIG. 11 shows a flowchart of another exemplary method for generating acompressed, or low-overhead, beacon.

FIG. 12 is a functional block diagram of another exemplary wirelessdevice that may be employed within the wireless communication system ofFIG. 1.

FIG. 13 shows a flowchart of an exemplary method for operating thewireless device of FIG. 2.

FIG. 14 is a functional block diagram of another exemplary wirelessdevice that may be employed within the wireless communication system ofFIG. 1.

FIG. 15 shows a flowchart of an exemplary method for communicating inthe wireless communication system of FIG. 1.

FIG. 16 is a functional block diagram of another exemplary wirelessdevice that may be employed within the wireless communication system ofFIG. 1.

FIG. 17 shows a flowchart of another exemplary method for communicatingin the wireless communication system of FIG. 1.

FIG. 18 is a functional block diagram of another exemplary wirelessdevice that may be employed within the wireless communication system ofFIG. 1.

DETAILED DESCRIPTION

Various aspects of the novel systems, apparatuses, and methods aredescribed more fully hereinafter with reference to the accompanyingdrawings. The teachings disclosure may, however, be embodied in manydifferent forms and should not be construed as limited to any specificstructure or function presented throughout this disclosure. Rather,these aspects are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the disclosure to thoseskilled in the art. Based on the teachings herein one skilled in the artshould appreciate that the scope of the disclosure is intended to coverany aspect of the novel systems, apparatuses, and methods disclosedherein, whether implemented independently of or combined with any otheraspect of the invention. For example, an apparatus may be implemented ora method may be practiced using any number of the aspects set forthherein. In addition, the scope of the invention is intended to coversuch an apparatus or method which is practiced using other structure,functionality, or structure and functionality in addition to or otherthan the various aspects of the invention set forth herein. It should beunderstood that any aspect disclosed herein may be embodied by one ormore elements of a claim.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Although some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description of the preferred aspects. Thedetailed description and drawings are merely illustrative of thedisclosure rather than limiting, the scope of the disclosure beingdefined by the appended claims and equivalents thereof.

Popular wireless network technologies may include various types ofwireless local area networks (WLANs). A WLAN may be used to interconnectnearby devices together, employing widely used networking protocols. Thevarious aspects described herein may apply to any communicationstandard, such as WiFi or, more generally, any member of the IEEE 802.11family of wireless protocols. For example, the various aspects describedherein may be used as part of the IEEE 802.11ah protocol, which usessub-1 GHz bands.

In some aspects, wireless signals in a sub-gigahertz band may betransmitted according to the 802.11ah protocol using orthogonalfrequency-division multiplexing (OFDM), direct-sequence spread spectrum(DSSS) communications, a combination of OFDM and DSSS communications, orother schemes. Implementations of the 802.11ah protocol may be used forsensors, metering, and smart grid networks. Advantageously, aspects ofcertain devices implementing the 802.11ah protocol may consume lesspower than devices implementing other wireless protocols, and/or may beused to transmit wireless signals across a relatively long range, forexample about one kilometer or longer.

In some implementations, a WLAN includes various devices which are thecomponents that access the wireless network. For example, there may betwo types of devices: access points (“APs”) and clients (also referredto as stations, or “STAs”). In general, an AP serves as a hub or basestation for the WLAN and an STA serves as a user of the WLAN. Forexample, an STA may be a laptop computer, a personal digital assistant(PDA), a mobile phone, etc. In an example, an STA connects to an AP viaa WiFi (e.g., IEEE 802.11 protocol such as 802.11ah) compliant wirelesslink to obtain general connectivity to the Internet or to other widearea networks. In some implementations an STA may also be used as an AP.

An access point (“AP”) may also include, be implemented as, or known asa NodeB, Radio Network Controller (“RNC”), eNodeB, Base StationController (“BSC”), Base Transceiver Station (“BTS”), Base Station(“BS”), Transceiver Function (“TF”), Radio Router, Radio Transceiver, orsome other terminology.

A station “STA” may also include, be implemented as, or known as anaccess terminal (“AT”), a subscriber station, a subscriber unit, amobile station, a remote station, a remote terminal, a user terminal, auser agent, a user device, user equipment, or some other terminology. Insome implementations an access terminal may include a cellulartelephone, a cordless telephone, a Session Initiation Protocol (“SIP”)phone, a wireless local loop (“WLL”) station, a personal digitalassistant (“PDA”), a handheld device having wireless connectioncapability, or some other suitable processing device connected to awireless modem. Accordingly, one or more aspects taught herein may beincorporated into a phone (e.g., a cellular phone or smartphone), acomputer (e.g., a laptop), a portable communication device, a headset, aportable computing device (e.g., a personal data assistant), anentertainment device (e.g., a music or video device, or a satelliteradio), a gaming device or system, a global positioning system device,or any other suitable device that is configured to communicate via awireless medium.

As discussed above, certain of the devices described herein mayimplement the 802.11ah standard, for example. Such devices, whether usedas an STA or AP or other device, may be used for smart metering or in asmart grid network. Such devices may provide sensor applications or beused in home automation. The devices may instead or in addition be usedin a healthcare context, for example for personal healthcare. They mayalso be used for surveillance, to enable extended-range Internetconnectivity (e.g. for use with hotspots), or to implementmachine-to-machine communications.

FIG. 1 illustrates an example of a wireless communication system 100 inwhich aspects of the present disclosure may be employed. The wirelesscommunication system 100 may operate pursuant to a wireless standard,for example the 802.11ah standard. The wireless communication system 100may include an AP 104, which communicates with STAs 106.

A variety of processes and methods may be used for transmissions in thewireless communication system 100 between the AP 104 and the STAs 106.For example, signals may be sent and received between the AP 104 and theSTAs 106 in accordance with OFDM/OFDMA techniques. If this is the case,the wireless communication system 100 may be referred to as anOFDM/OFDMA system. Alternatively, signals may be sent and receivedbetween the AP 104 and the STAs 106 in accordance with CDMA techniques.If this is the case, the wireless communication system 100 may bereferred to as a CDMA system.

A communication link that facilitates transmission from the AP 104 toone or more of the STAs 106 may be referred to as a downlink (DL) 108,and a communication link that facilitates transmission from one or moreof the STAs 106 to the AP 104 may be referred to as an uplink (UL) 110.Alternatively, a downlink 108 may be referred to as a forward link or aforward channel, and an uplink 110 may be referred to as a reverse linkor a reverse channel.

The AP 104 may act as a base station and provide wireless communicationcoverage in a basic service area (BSA) 102. The AP 104 along with theSTAs 106 associated with the AP 104 and that use the AP 104 forcommunication may be referred to as a basic service set (BSS). It shouldbe noted that the wireless communication system 100 may not have acentral AP 104, but rather may function as a peer-to-peer networkbetween the STAs 106. Accordingly, the functions of the AP 104 describedherein may alternatively be performed by one or more of the STAs 106.

The AP 104 may transmit a beacon signal (or simply a “beacon”), via acommunication link such as the downlink 108, to other nodes of thesystem 100, which may help the other nodes STAs 106 to synchronize theirtiming with the AP 104, or which may provide other information orfunctionality. Such beacons may be transmitted periodically. In oneaspect, the period between successive transmissions may be referred toas a superframe. Transmission of a beacon may be divided into a numberof groups or intervals. In one aspect, the beacon may include, but isnot limited to, such information as timestamp information to set acommon clock, a peer-to-peer network identifier, a device identifier,capability information, a superframe duration, transmission directioninformation, reception direction information, a neighbor list, and/or anextended neighbor list, some of which are described in additional detailbelow. Thus, a beacon may include information both common (e.g. shared)amongst several devices, and information specific to a given device.

In some aspects, a STA may be required to associate with the AP in orderto send communications to and/or receive communications from the AP. Inone aspect, information for associating is included in a beaconbroadcast by the AP. To receive such beacon, the STA may perform a broadcoverage search over a coverage region, for example. A search may alsobe performed by the STA by sweeping a coverage region in a lighthousefashion, for example. After receiving the information for associating,the STA may transmit a reference signal, such as an association probe orrequest, to the AP. In some aspects, the AP may use backhaul services,for example, to communicate with a larger network, such as the Internetor a public switched telephone network (PSTN).

FIG. 2 illustrates various components that may be utilized in a wirelessdevice 202 that may be employed within the wireless communication system100. The wireless device 202 is an example of a device that may beconfigured to implement the various methods described herein. Forexample, the wireless device 202 may include the AP 104 or one of theSTAs 106.

The wireless device 202 may include a processor 204 which controlsoperation of the wireless device 202. The processor 204 may also bereferred to as a central processing unit (CPU). The memory 206, whichmay include both read-only memory (ROM) and random access memory (RAM),provides instructions and data to the processor 204. A portion of thememory 206 may also include non-volatile random access memory (NVRAM).The processor 204 typically performs logical and arithmetic operationsbased on program instructions stored within the memory 206. Theinstructions in the memory 206 may be executable to implement themethods described herein.

When the wireless device 202 is implemented or used as an AP, theprocessor 204 may be configured to select one of a plurality of beacontypes, and to generate a beacon signal having that beacon type. Forexample, the processor 204 may be configured to generate a beacon signalincluding beacon information and to determine what type of beaconinformation to use, as discussed in further detail below.

When the wireless device 202 is implemented or used as a STA, theprocessor 204 may be configured to process beacon signals of a pluralityof different beacon types. For example, the processor 204 may beconfigured to determine the type of beacon used in a beacon signal andto process the beacon and/or fields of the beacon signal accordingly asfurther discussed below.

The processor 204 may include or be a component of a processing systemimplemented with one or more processors. The one or more processors maybe implemented with any combination of general-purpose microprocessors,microcontrollers, digital signal processors (DSPs), field programmablegate array (FPGAs), programmable logic devices (PLDs), controllers,state machines, gated logic, discrete hardware components, dedicatedhardware finite state machines, or any other suitable entities that canperform calculations or other manipulations of information.

The processing system may also include machine-readable media forstoring software. Software shall be construed broadly to mean any typeof instructions, whether referred to as software, firmware, middleware,microcode, hardware description language, or otherwise. Instructions mayinclude code (e.g., in source code format, binary code format,executable code format, or any other suitable format of code). Theinstructions, when executed by the one or more processors, cause theprocessing system to perform the various functions described herein.

The wireless device 202 may also include a housing 208 that may includea transmitter 210 and/or a receiver 212 to allow transmission andreception of data between the wireless device 202 and a remote location.The transmitter 210 and receiver 212 may be combined into a transceiver214. An antenna 216 may be attached to the housing 208 and electricallycoupled to the transceiver 214. The wireless device 202 may also include(not shown) multiple transmitters, multiple receivers, multipletransceivers, and/or multiple antennas.

The transmitter 210 may be configured to wirelessly transmit beaconsignals having different beacon types. For example, the transmitter 210may be configured to transmit beacon signals with different types ofbeacons generated by the processor 204, discussed above.

The receiver 212 may be configured to wirelessly receive beacon signalshaving different beacon types. In some aspects, the receiver 212 isconfigured to detect a type of a beacon used and to process the beaconsignal accordingly, as discussed in further detail below.

The wireless device 202 may also include a signal detector 218 that maybe used in an effort to detect and quantify the level of signalsreceived by the transceiver 214. The signal detector 218 may detect suchsignals as total energy, energy per subcarrier per symbol, powerspectral density and other signals. The wireless device 202 may alsoinclude a digital signal processor (DSP) 220 for use in processingsignals. The DSP 220 may be configured to generate a packet fortransmission. In some aspects, the packet may include a physical layerdata unit (PPDU).

The wireless device 202 may further include a user interface 222 in someaspects. The user interface 222 may include a keypad, a microphone, aspeaker, and/or a display. The user interface 222 may include anyelement or component that conveys information to a user of the wirelessdevice 202 and/or receives input from the user.

The wireless device 202 may further include a power supply 230 in someaspects. The power supply 230 may include a wired power supply, abattery, capacitor, etc. The power supply 230 may be configured toprovide various levels of power output. In some embodiments, othercomponents of the wireless device 202 may be configured to enter one ormore different power consumption states. For example, the processor 204may be configured to operate in a high-power or low-power mode.Likewise, the transmitter 219 and receiver 212 may be capable ofoperating in various power states, which may include a disabled state, afull power state, and one or more states in between. Particularly, thedevice 202 on a whole may be configured to enter a relatively low powerstate in between transmissions, and enter a relatively high power stateat one or more determined times.

The various components of the wireless device 202 may be coupledtogether by a bus system 226. The bus system 226 may include a data bus,for example, as well as a power bus, a control signal bus, and a statussignal bus in addition to the data bus. Those of skill in the art willappreciate the components of the wireless device 202 may be coupledtogether or accept or provide inputs to each other using some othermechanism.

Although a number of separate components are illustrated in FIG. 2,those of skill in the art will recognize that one or more of thecomponents may be combined or commonly implemented. For example, theprocessor 204 may be used to implement not only the functionalitydescribed above with respect to the processor 204, but also to implementthe functionality described above with respect to the signal detector218 and/or the DSP 220. Further, each of the components illustrated inFIG. 2 may be implemented using a plurality of separate elements.

As discussed above, the wireless device 202 may include an AP 104 or anSTA 106, and may be used to transmit and/or receive communicationsincluding beacon signals. For ease of reference, when the wirelessdevice 202 is configured as an AP, it is hereinafter referred to as awireless device 202 a. Similarly, when the wireless device 202 isconfigured as a STA, it is hereinafter referred to as a wireless device202 s.

FIG. 3 illustrates an example of a beacon frame 300 used in legacysystems for communication. As shown, the beacon 300 includes a medianaccess control (MAC) header 302, a frame body 304, and a frame controlsequence (FCS) 306. As shown, the MAC header 302 is 24 bytes long, theframe body 304 is of variable length, and the FCS 306 is four byteslong.

The MAC header 302 serves to provide basic routing information for thebeacon frame 300. In the illustrated embodiment, the MAC header 302includes a frame control (FC) field 308, a duration field 310, adestination address (DA) field 312, a source address (SA) field 314, abasic service set identification (BSSID) field 316, and a sequencecontrol field 318. As shown, the FC field 308 is two bytes long, theduration field 310 is two bytes long, the DA field 312 is six byteslong, the SA field 314 is six bytes long, the BSSID field 316 is sixbytes long, and the sequence control field 318 is two bytes long.

The frame body 304 serves to provide detailed information about thetransmitting node. In the illustrated embodiment, the frame body 304includes a timestamp field 320, a beacon interval field 322, acapability information field 324, a service set identifier (SSID) field326, a supported rates field 328, a frequency-hopping (FH) parameter set330, a direct-sequence parameter set 332, a contention-free parameterset 334, an independent basic service set (IBSS) parameter set 336, acountry information field 338, a FH hopping parameter field 340, a FHpattern table 342, a power constraint field 344, a channel switchannouncement field 346, a quiet field 348, a IBSS direct frequencyselection (DFS) field 350, a transmit power control (TPC) field 352, aneffective radiated power (ERP) information field 354, an extendedsupported rates field 356, and a robust security network (RSN) field358.

As shown in FIG. 3, the timestamp field 320 is eight bytes long, thebeacon interval field 322 is two bytes long, the capability informationfield 324 is two bytes long, the service set identifier (SSID) field 326is a variable length, the supported rates field 328 is a variablelength, the frequency-hopping (FH) parameter set 330 is seven byteslong, the direct-sequence parameter set 332 is two bytes long, thecontention-free parameter set 334 is eight bytes long, an independentbasic service set (IBSS) parameter set 336 is 4 bytes long, the countryinformation field 338 is a variable length, the FH hopping parameterfield 340 is four bytes long, the FH pattern table 342 is a variablelength, the power constraint field 344 is three bytes long, the channelswitch announcement field 346 is six bytes long, the quiet field 348 iseight bytes long, the IBSS direct frequency selection (DFS) field 350 isa variable length, the transmit power control (TPC) field 352 is fourbytes long, an effective radiated power (ERP) information field 354 isthree bytes long, an extended supported rates field 356 is a variablelength, and the robust security network (RSN) field 358 is a variablelength.

Referring still to FIG. 3, although the beacon frame 300 is a variablelength, it is always at least 89 bytes long. In various radioenvironments, much of the information contained in the beacon frame 300may be used infrequently or not at all. Accordingly, in low-power radioenvironments, it may be desirable to reduce the length of the beaconframe 300 in order to reduce power consumption. Moreover, some radioenvironments use low data rates. For example an access pointimplementing an 802.11ah standard may take a relatively long time totransmit the beacon frame 300 due to relatively slow data transmissionrates. Accordingly, it may be desirable to reduce the length of thebeacon frame 300 in order to shorten the amount of time it takes totransmit the beacon frame 300.

There are a number of approaches by which the beacon frame 300 can beshortened or compressed. In an embodiment, one or more fields of thebeacon frame 300 can be omitted. In another embodiment, one or morefields of the beacon frame 300 can be reduced in size, for example byusing a different encoding scheme or by accepting lower informationcontent. In one embodiment, the wireless system can allow a STA to querythe AP for information omitted from a beacon. For example, the STA canrequest information omitted from the beacon via a probe request. In anembodiment, a full beacon can be sent periodically or at a dynamicallychosen time.

FIG. 4 illustrates an example low-overhead beacon frame 400. In theillustrated embodiment, the low-overhead beacon frame 400 includes aframe control (FC) field 410, a source address (SA) field 420, atimestamp 430, a change sequence field 440, a next full beacon timeindication (NFBTI) 450, a compressed SSID field 460, an access networkoptions field 470, an optional IE field 480, and a cyclic redundancycheck (CRC) field 490. As shown, the frame control (FC) field 410 is twobytes long, the source address (SA) field 420 is six bytes long, thetimestamp 430 is four bytes long, the change sequence field 440 is onebyte long, the duration to next full beacon field 450 is three byteslong, the compressed SSID field 460 is four bytes long, the accessnetwork options field 470 is one byte long, and the cyclic redundancycheck (CRC) field 490 is four bytes long.

In various embodiments, the low-overhead beacon frame 400 can omit oneor more fields shown in FIG. 4 and/or include one or more fields notshown in FIG. 4, including any of the fields discussed herein.Particularly, in various embodiments, one or more of the next fullbeacon time indication 450, the compressed SSID field 460, and theaccess network options field 470 can be omitted in accordance one ormore flags in the frame control field 410. A person having ordinaryskill in the art will appreciate that the fields in the low-overheadbeacon frame 400 can be of different suitable lengths, and can be in adifferent order.

The destination address (DA) field 312, described above with respect toFIG. 3, can be omitted from the low-overhead beacon frame 400 becausethe beacon frame 400 can be broadcast. Accordingly, there may be no needto identify a specific destination address. Similarly, the BSSID field316 can be omitted. In an embodiment, the SA field 420 can include theBSSID. The duration field 310 can also be omitted. In an embodiment, ifa net allocation vector (NAV) is desired after sending the low-overheadbeacon frame 400, it can be signaled using the short interframe space(SIFS) after the beacon frame 400 is sent. Furthermore, the sequencecontrol field 318 can be omitted from the low-overhead beacon frame 400because sequence control may be unnecessary in a beacon.

In the illustrated embodiment, the frame control (FC) field 410 includesa two-bit version field 411, a two-bit type field 412, a four-bitsubtype field 413, a one-bit next fill beacon time indication presentflag 414, a one-bit SSID present flag 415, a one-bit internetworkingpresent flag 416, a three-bit bandwidth (BW) field 417, a one-bitsecurity flag 418, and one reserved (RSVD) bit 419. In variousembodiments, the FC field 410 can omit one or more fields shown in FIG.4 and/or include one or more fields not shown in FIG. 4, including anyof the fields discussed herein. A person having ordinary skill in theart will appreciate that the fields in the beacon FC field 410 can be ofdifferent suitable lengths, and can be in a different order.

In an embodiment, the frame control (FC) field 410 contains a flagindicating that the beacon frame 400 is a low-overhead beacon (LOB),also referred to as a “short beacon.” In an embodiment, the FC field 410can indicate that the beacon frame 400 is a short beacon by setting thetype field 412 to “11” (which can indicate a beacon frame) and bysetting the subtype field 413 to “0001” (which can indicate that thebeacon is compressed, low-overhead, and/or “short”). When a STA receivesthe beacon frame 400, it can decode the FC field 410 containing the flagindicating that the beacon frame 400 is a short beacon. Accordingly, theSTA can decode the beacon frame 400 in accordance with the formatdescribed herein.

The next full beacon time indication present flag 414 shown in FIG. 4includes one bit. In some implementations, the next full beacon timeindication present flag 414 may include more than one bit. In someimplementations, the next full beacon time indication present flag 414may include a configurable number of bits. For example, the length ofthe next full beacon time present indication field 414 may be associatedwith device specific characteristics such as a service set, device type,or a value stored in memory.

The value included in the next full beacon time indication present flag414 may be used to identify that the next full beacon time indicationfield 450 is included in the low-overhead beacon frame 400. Accordingly,a transmitting device, such as the AP 104 (FIG. 1), may set a value inthe next full beacon time indication present flag 414 when thetransmitting device is configured to transmit a next full beacon timeindication field 450 and will be including the next full beacon timeindication field 450 in a transmitted frame. For example, in theimplementation shown in FIG. 4, the next full beacon time indicationpresent flag 414 including one bit may set the value of the next fullbeacon time indication present flag 414 to “1” to indicate that thelow-overhead beacon frame 400 includes a next full beacon timeindication field 450. Conversely, the transmitting device may beconfigured to set the value of the next full beacon time indicationpresent flag 414 to “0” to indicate that the low-overhead beacon frame400 does not include a next full beacon time indication field 450.

In some implementations, “presence” of the next full beacon timeindication field may also include whether the value included in the nextfull beacon time indication field is an operational value. For example,in some implementations, if the transmitting device is not configured togenerate a next full beacon time indication value for each signal, thetransmitting device may set the value for the field to an arbitraryvalue (e.g., random, constant, null). Accordingly, setting the presencevalue such that an indication of “not present” is provided may, in someimplementations, mean the field is included in the frame but the valuecontained in the field is non-operational (e.g., arbitrary).

A receiving device, such as the STA 106 (FIG. 1), may process the framecontrol field 410 to determine whether the received frame includes anext full beacon time indication field 450 by identifying the valueincluded in the next full beacon time indication present flag 414. Forexample, in the implementation shown in FIG. 4, the next full beacontime indication present flag 414 including one bit may set the value ofthe next full beacon time indication present flag 414 to “1” to indicatethat the low-overhead beacon frame 400 includes a next full beacon timeindication field 450. Conversely, the value of the next full beacon timeindication present flag 414 may be set to “0” to indicate that thelow-overhead beacon frame 400 does not include a next full beacon timeindication field 450. In some implementations, the receiving device mayalter the processing of the low-overhead beacon frame 400 based onwhether the low-overhead beacon frame 400 includes a next full beacontime indication field 450. For example, if the receiving deviceidentifies whether the frame includes a next full beacon time indicationfield 450, via processing of the next full beacon time indicationpresent flag 414 included in the frame control field 410, an appropriatesignal processor may be configured to process the frames with or withouta next full beacon time indication field 450. This can improve theprocessing of the frame because the receiving device may identifycharacteristics of the frame (e.g., presence of the next full beacontime indication) without necessarily processing the entire frame first.

The SSID present flag 415 shown in FIG. 4 includes one bit. In someimplementations, the SSID present flag 415 may include more than onebit. In some implementations, the SSID present flag 415 may include aconfigurable number of bits. For example, the length of the SSID presentflag 415 may be associated with device specific characteristics such asa service set, device type, or a value stored in memory.

The value included in the SSID present flag 415 may be used to identifythat the compressed SSID field 460 is included in the low-overheadbeacon frame 400. For example, in some implementations, the SSID can behidden or cloaked. Accordingly, a transmitting device, such as the AP104 (FIG. 1), may set a value in the SSID present flag 415 when thetransmitting device is configured to transmit a compressed SSID field460 and will be including the compressed SSID field 460 in a transmittedframe. For example, in the implementation shown in FIG. 4, the SSIDpresent flag 415 including one bit may set the value of the SSID presentflag 415 to “1” to indicate that the low-overhead beacon frame 400includes a compressed SSID field 460. Conversely, the transmittingdevice may be configured to set the value of the SSID present flag 415to “0” to indicate that the low-overhead beacon frame 400 does notinclude a compressed SSID field 460.

In some implementations, “presence” of the compressed SSID field mayalso include whether the value included in the compressed SSID field isan operational value. For example, in some implementations, if thetransmitting device is not configured to generate a compressed SSIDfield value for each signal, the transmitting device may set the valuefor the field to an arbitrary value (e.g., random, constant, null).Accordingly, setting the presence value such that an indication of “notpresent” is provided may, in some implementations, mean the field isincluded in the frame but the value contained in the field isnon-operational (e.g., arbitrary).

A receiving device, such as the STA 106 (FIG. 1), may process the framecontrol field 410 to determine whether the received frame includes acompressed SSID field 460 by identifying the value included in the SSIDpresent flag 415. For example, in the implementation shown in FIG. 4,the SSID present flag 415 including one bit may set the value of theSSID present flag 415 to “1” to indicate that the low-overhead beaconframe 400 includes a compressed SSID field 460. Conversely, the value ofthe SSID present flag 415 may be set to “0” to indicate that thelow-overhead beacon frame 400 does not include a compressed SSID field460. In some implementations, the receiving device may alter theprocessing of the low-overhead beacon frame 400 based on whether thelow-overhead beacon frame 400 includes a compressed SSID field 460. Forexample, if the receiving device identifies whether the frame includes acompressed SSID field 460, via processing of the SSID present flag 415included in the frame control field 410, an appropriate signal processormay be configured to process the frames with or without a compressedSSID field 460. This can improve the processing of the frame because thereceiving device may identify characteristics of the frame (e.g.,presence of the compressed SSID field) without necessarily processingthe entire frame first.

In one embodiment, the AP can set the compressed SSID field 460 to areserved value indicating that the SSID is hidden. For example, when theSSID is hidden, the compressed SSID field 460 can have a value of allzeroes, all ones, etc. If the SSID hashes to the reserved value whencomputed using the SSID hash function, the hashed SSID can be remappedto another value (e.g., constant value), or remapped to an alternativevalue using an alternative hashing function. In another embodiment, theFC field 410 can include an indication that the SSID is hidden.

The internetworking present flag 416 shown in FIG. 4 includes one bit.In some implementations, the internetworking present flag 416 mayinclude more than one bit. In some implementations, the internetworkingpresent flag 416 may include a configurable number of bits. For example,the length of the next full beacon time present indication field 414 maybe associated with device specific characteristics such as a serviceset, device type, or a value stored in memory.

The value included in the internetworking present flag 416 may be usedto identify that the access network options field 470 is included in thelow-overhead beacon frame 400. Accordingly, a transmitting device, suchas the AP 104 (FIG. 1), may set a value in the internetworking presentflag 416 when the transmitting device is configured to transmit anaccess network options field 470 and will be including the accessnetwork options field 470 in a transmitted frame. For example, in theimplementation shown in FIG. 4, the internetworking present flag 416including one bit may set the value of the internetworking present flag416 to “1” to indicate that the low-overhead beacon frame 400 includesan access network options field 470. Conversely, the transmitting devicemay be configured to set the value of the internetworking present flag416 to “0” to indicate that the low-overhead beacon frame 400 does notinclude an access network options field 470.

In some implementations, “presence” of the access network options fieldmay also include whether the value included in the access networkoptions field is an operational value. For example, in someimplementations, if the transmitting device is not configured togenerate an access network options value for each signal, thetransmitting device may set the value for the field to an arbitraryvalue (e.g., random, constant, null). Accordingly, setting the presencevalue such that an indication of “not present” is provided may, in someimplementations, mean the field is included in the frame but the valuecontained in the field is non-operational (e.g., arbitrary).

A receiving device, such as the STA 106 (FIG. 1), may process the framecontrol field 410 to determine whether the received frame includes anaccess network options field 470 by identifying the value included inthe internetworking present flag 416. For example, in the implementationshown in FIG. 4, the internetworking present flag 416 including one bitmay set the value of the internetworking present flag 416 to “1” toindicate that the low-overhead beacon frame 400 includes an accessnetwork options field 470. Conversely, the value of the internetworkingpresent flag 416 may be set to “0” to indicate that the low-overheadbeacon frame 400 does not include an access network options field 470.In some implementations, the receiving device may alter the processingof the low-overhead beacon frame 400 based on whether the low-overheadbeacon frame 400 includes an access network options field 470. Forexample, if the receiving device identifies whether the frame includesan access network options field 470, via processing of theinternetworking present flag 416 included in the frame control field410, an appropriate signal processor may be configured to process theframes with or without an access network options field 470. This canimprove the processing of the frame because the receiving device mayidentify characteristics of the frame (e.g., presence of the accessnetwork options) without necessarily processing the entire frame first.

In an embodiment, the bandwidth field 417 serves to indicate a bandwidthof the AP 104 (FIG. 1). In an embodiment, the bandwidth field 417 canindicate a bandwidth of 2 MHz times the binary value of the bandwidthfield 417. For example, a value of “0001” can indicate a 2 MHz BSS and avalue of “0002” can indicate a 4 MHz BSS. In an embodiment, a value of“0000” can indicate 1 MHz BSS. In various embodiments, other multipliersand/or encodings can be used.

The security flag 418 shown in FIG. 4 includes one bit. In someimplementations, the security flag 418 may include more than one bit. Insome implementations, the security flag 418 may include a configurablenumber of bits. For example, the length of the security flag 418 may beassociated with device specific characteristics such as a service set,device type, or a value stored in memory.

In an embodiment, the value included in the security flag 418 can serveto indicate whether data encryption is used by the AP 104 (FIG. 1). Inan embodiment, details of a robust security network (RSN) can beobtained from a probe response. Accordingly, a transmitting device, suchas the AP 104 (FIG. 1), may set a value in the security flag 418 whenthe transmitting device is configured to use data encryption. Forexample, in the implementation shown in FIG. 4, the security flag 418including one bit may set the value of the security flag 418 to “1” toindicate that the transmitting device is configured to use dataencryption. Conversely, the transmitting device may be configured to setthe value of the security flag 418 to “0” to indicate that thetransmitting device is not configured to use data encryption.

A receiving device, such as the STA 106 (FIG. 1), may process the framecontrol field 410 to determine whether the transmitting device isconfigured to use data encryption by identifying the value included inthe security flag 418. For example, in the implementation shown in FIG.4, the security flag 418 including one bit may set the value of thesecurity flag 418 to “1” to indicate that the transmitting device isconfigured to use data encryption. Conversely, the value of the securityflag 418 may be set to “0” to indicate that the transmitting device isnot configured to use data encryption. In some implementations, thereceiving device may alter the processing of the low-overhead beaconframe 400 and/or other frames based on whether that the transmittingdevice is configured to use data encryption. For example, if thereceiving device identifies whether the transmitting device isconfigured to use data encryption, via processing of the security flag418 included in the frame control field 410, an appropriate signalprocessor may be configured to process the frames with or withoutencryption.

In the illustrated embodiment of FIG. 4, the timestamp field 430 isshorter than the timestamp field 320 described above with respect toFIG. 3. Specifically, the timestamp field 430 is only four bytes long,whereas the timestamp field 320 is eight bytes long. The timestamp field430 can include one or more least-significant-bits of a “full”timestamp, such as the timestamp field 320. For example, the timestampfield 430 can include the four least significant bytes of the timestampfield 320.

In an embodiment, a STA receiving the low-overhead beacon 400 canretrieve a complete eight-byte timestamp from a transmitting AP via aprobe request. In one embodiment, the length of the timestamp field 430can be chosen such that the timestamp field 430 will not overflow morethan once every seven minutes. In a conventional system, the timestampfield 320 value is interpreted as a number of nanoseconds. In anembodiment, the timestamp field 430 value can be interpreted as a numberof OFDM symbol periods. Accordingly, in embodiments where an OFDM symbolperiod is longer than a nanosecond, the timestamp field 430 may notoverflow as quickly.

In an embodiment, the timestamp field 430 can facilitate a timingsynchronization function (TSF) between devices 104 and 106 in thewireless communication system 100. In embodiments where the AP 104updates the timestamp field 430 at 1 MHz, a four-byte timestamp field430 will overflow approximately every 72 minutes. In embodiments wheredevice clocks drive at about +/−20 ppm, it would take approximately 1.4years to drive by 30 min. Accordingly, a device 106 can maintain timesynchronization with the AP 104 if it checks the beacon 400 as rarely asonce a day.

In the illustrated embodiment of FIG. 4, the change sequence field 440can serve to provide a sequence number indicative of a change in networkinformation. In the illustrated embodiment, the change sequence field440 serves keep track of changes to the AP 104. In an embodiment, the AP104 may increment the change sequence field 440 when one or moreparameters of the AP 104 change. For example, the AP may transmit a fullbeacon when the SSID changes. In one embodiment, the AP 104 maydecrement the change sequence field 440, change the change sequencefield 440 to a random or pseudorandom number, or otherwise modify thechange sequence field 440 when the configuration of the AP 104 changes.In various embodiments, the change sequence field 440 may be referred toas a beacon index or a beacon number.

The STA 106 can be configured to detect a change in the change sequencefield 440. When the STA 106 detects the change in the change sequencefield 440, the STA 106 may wait for the transmission of a full beacon.The STA 106 may delay transitioning to a sleep or low-power mode whileit waits for the AP 104 to transmit a full beacon. In anotherembodiment, the STA 106 may send a probe request frame to the AP 104when the STA 106 detects the change in the change sequence field 440.The AP 104 may send updated configuration information to the STA 106 inresponse to the probe request frame.

Referring still to FIG. 4, the next full beacon time indication 450 canserve to indicate the next time at which the AP 104 will transmit a fullbeacon, such as the beacon 300. Accordingly, in an embodiment, STAs 106may avoid probe request transmission, and can sleep while waiting forthe full beacon. In various embodiments, the next full beacon timeindication 450 can include one or more of: a flag indicating that a fullbeacon will follow, an absolute time at which the AP 104 will transmitthe full beacon, and a duration until the AP 104 will transmit the fullbeacon.

In the illustrated embodiment, the next full beacon indication 450 caninclude a next full beacon time indicator. In an embodiment, a STA canuse the duration next full beacon time indicator to determine a time towake up and receive a full beacon, thereby saving power. In theillustrated embodiment, the next full beacon time indicator includes the3 most significant bytes, of the 4 least significant bytes, of a nexttarget beacon transmit time (TBTT) timestamp. In other words, the nextfull beacon time indication 450 can include bytes 1 through 4 of thenext TBTT timestamp, with byte 0 omitted (in a little endian notation).In an embodiment, the next full beacon time indication 450 can have aresolution in units of 46 μs. In an embodiment, the AP 104 can computethe next TBTT in software, and store the value in the frame. In variousembodiments, the next full beacon time indication 450 can be encoded inother manners.

In an embodiment, the next full beacon time indication 450 can include afull beacon follows flag. The full beacon follows flag can include onebit. In some implementations, the full beacon follows flag may includemore than one bit. In some implementations, the full beacon follows flagmay include a configurable number of bits. For example, the length ofthe security flag 418 may be associated with device specificcharacteristics such as a service set, device type, or a value stored inmemory. The full beacon follows flag can serve to indicate that the AP104 will transmit a conventional beacon, such as the beacon frame 300described above with respect to FIG. 3, after transmitting thelow-overhead beacon 400. In an embodiment, the AP 104 transmits a fullbeacon when the AP's 104 configuration changes. For example, the AP 104may transmit a full beacon when the SSID changes.

In an embodiment, the next full beacon time indication 450 can include aduration to next full beacon. The duration to next full beacon can serveto indicate the number of time units (TUs) before the next full beacon.In an embodiment, time units can be 1024 μs. In an embodiment, theduration to next full beacon can indicate the number of time unitsbefore the next full beacon to within an accuracy of 1 TU. In anembodiment, a STA can use the duration to the next full beacon todetermine a time to wake up and receive a full beacon, thereby savingpower. In an embodiment, a preset value (such as a null value) in thenext full beacon time indication 450 can indicate that the duration tonext full beacon feature is not supported, or that the duration is notdetermined. For example, a value of all zeroes, all ones, and/or anyother predetermined value can indicate that the AP does not supportproviding the duration to the next full beacon, or that the duration isnot determined. In various embodiments, the duration to next full beaconcan be encoded in other manners.

In the illustrated embodiment of FIG. 4, the compressed SSID field 460can serve a similar purpose to the SSID field 344, described above withrespect to FIG. 3. Specifically, compressed SSID field 460 can identifya wireless network. Whereas the SSID field 344 includes avariable-length alphanumeric string, however, the compressed SSID field460 can be shorter. For example, the compressed SSID field 460 caninclude just four bytes. In an embodiment, the compressed SSID field 460is a hash of the SSID of an access point such as, for example, the SSIDhash field 430 described above with respect to FIG. 4. In an embodiment,the compressed SSID field 460 can be a CRC computed on a portion of, orall of, the SSID associated with the AP 104. For example, the compressedSSID field 460 can use the same generator polynomial that is used forcalculating the CRC checksum 490.

In an embodiment, a STA can request the full SSID from an APtransmitting the low-overhead beacon frame 400 via a probe request. Inanother embodiment, a STA searching for a particular SSID can determinewhether the AP matches the desired SSID by hashing the desired SSID andcomparing the result with the compressed SSID field 460. In anembodiment, the length of the compressed SSID field 460 can be chosensuch that the chances of two different network SSIDs hashing to the samevalue is less than 0.5%.

Referring still to FIG. 4, the access network options field 470 caninclude access services provided by the AP 104. For example, the accessnetwork options field 470 can include a 4-bit access network type field,a one-bit internet flag, a one-bit additional step required for access(ASRA) flag, one-bit emergency services reachable (ESR) flag, and aone-bit unauthenticated emergency service accessible (UESA) flag. Theaccess network options field 470 can help STAs filter out undesired APsin all scanning channels quickly, based on the frequently transmittedcompressed beacon 400, without wasting time and/or power to track fullbeacons 300 or probe responses from the APs.

Referring still to FIG. 4, the optional IE field 480 can includeadditional information elements, as will be described herein. In oneembodiment, the optional IE field 480 includes a full TIM or TIM followsindicator. In another embodiment, the optional IE field 480 includesadditional beacon information.

Referring still to FIG. 4, the CRC field 490 can serve a purpose similarto that of the FCS field 306 described above with respect to FIG. 3.Specifically, the CRC field 490 can allow a receiving STA to identifytransmission errors in a received beacon. Although the CRC field 490 isshown as four bytes long, the CRC field 490 can be different lengths invarious embodiments. In one embodiment, for example, the CRC field 490is two bytes long. In another embodiment, the CRC field 490 is one bytelong. The CRC field 490 can be another type of check code. In anembodiment, the CRC field 490 is a message integrity check (MIC).

In an embodiment, the low-overhead beacon frame 400 can be referred toas an “SSID short beacon.” The SSID short beacon 400 can be broadcast(for example, by the AP 104 shown in FIG. 1) to at least onenon-associated STA 106. The SSID short beacon 400 can serve to advertisean SSID (or the compressed SSID 430) to non-associated STAs 106, whichmay be searching for a network. In an embodiment, the AP 104 transmitsthe SSID short beacon 400 at an SSID short beacon interval. The SSIDshort beacon interval can be a multiple of the beacon interval field ofa full beacon (a “full beacon interval” such as, for example, the beaconinterval field 322 discussed above with respect to FIG. 3). For example,the SSID short beacon interval can be 1 times the full beacon interval,2 times the full beacon interval, 3 times the full beacon interval, etc.

In an embodiment, the frame control (FC) field 410 contains a flagindicating that the beacon frame 400 is a low-overhead beacon (LOB),also referred to as a “short beacon” and more specifically an “SSIDshort beacon.” In an embodiment, the FC field 410 can indicate that thebeacon frame 400 is an SSID short beacon by setting a “type value”(which can be bits B3:B2 of the FC field 410) to “11” (which canindicate a beacon frame) and by setting a “subtype value” (which can bebits B7:B4 of the FC field 410) to “0001” (which can indicate that thebeacon is compressed, low-overhead, “short,” and/or targeted atunassociated STAs). When a STA receives the beacon frame 400, it candecode the FC field 410 containing the flag indicating that the beaconframe 400 is an SSID short beacon. Accordingly, the STA can decode thebeacon frame 400 in accordance with the format described herein. Asdiscussed above, the STA receiving the SSID short beacon may beunassociated with the AP transmitting the SSID short beacon.

In an embodiment, an access point may periodically send a bitmap (i.e.,the TIM) within a beacon to identify which stations using power savingmode have data frames waiting for them in the access point's buffer. TheTIM identifies a station by an association ID (AID) that the accesspoint assigns during the association process. In various low-trafficand/or low-power network environments, however, it may not be desirableto periodically send the TIM. For example, in electronic price tagapplications, an electronic price display may update only once an hour.Therefore, sending a TIM every TIM interval (which is conventionallymuch shorter than once an hour) may be wasteful. In embodiments where aTIM is not sent every TIM interval, however, the TIM interval ispreferentially small so that when an update does occur, it can becommunicated swiftly.

FIG. 5 illustrates another example low-overhead beacon frame 500. In theillustrated embodiment, the low-overhead beacon frame 500 includes aframe control (FC) field 510, a source address (SA) field 520, atimestamp 540, a change sequence field 550, a traffic indication map(TIM) information element (IE) 566, and a cyclic redundancy check (CRC)field 580. As shown, the frame control (FC) field 510 is two bytes long,the source address (SA) field 520 is six bytes long, the timestamp 540is four bytes long, the change sequence field 550 is one byte long, theTIM IE field 566 is a variable length, and the cyclic redundancy check(CRC) field 580 is four bytes long. In various embodiments, thelow-overhead beacon frame 500 can omit one or more fields shown in FIG.5 and/or include one or more fields not shown in FIG. 5, including anyof the fields discussed herein. A person having ordinary skill in theart will appreciate that the fields in the low-overhead beacon frame 500can be of different suitable lengths, and can be in a different order.

In an embodiment, the low-overhead beacon frame 500 can be referred toas a “TIM short beacon.” The TIM short beacon 500 can be broadcast (forexample, by the AP 104 shown in FIG. 1) to at least one associated STA106. The TIM short beacon 500 can serve to provide a timestamp for STAsto maintain synchronization, and/or a change sequence to indicate whennetwork information has changed. In an embodiment, the AP 104 transmitsthe TIM short beacon 500 at a TIM short beacon interval. The TIM shortbeacon interval can be a multiple of the beacon interval field of a fullbeacon (a “full beacon interval” such as, for example, the beaconinterval field 322 discussed above with respect to FIG. 3). For example,the TIM short beacon interval can be 1 times the full beacon interval, 2times the full beacon interval, 3 times the full beacon interval, etc.

In an embodiment, the TIM short beacon interval can be different fromthe SSID short beacon interval discussed above with respect to FIG. 4.In an embodiment, the AP 104 may be configured to transmit one or moreof the SSID short beacon 400, the TIM short beacon 500, and a fullbeacon at a target beacon transmit time (TBTT), in accordance with theSSID short beacon interval, the TIM short beacon interval, and the fullbeacon interval, respectively. In an embodiment, when the AP 104transmits both the SSID short beacon 400 and the TIM short beacon 500,the AP 104 transmits the TIM short beacon 500 first, followed by theSSID short beacon 400 within the SIFS time.

The destination address (DA) field 312, described above with respect toFIG. 3, can be omitted from the low-overhead beacon frame 500 becausethe beacon frame 500 can be broadcast. Accordingly, there may be no needto identify a specific destination address. Similarly, the BSSID field316 can be omitted. The duration field 310 can also be omitted. In anembodiment, if a net allocation vector (NAV) is desired after sendingthe low-overhead beacon frame 500, it can be signaled using the shortinterframe space (SIFS) after the beacon frame 500 is sent. Furthermore,the sequence control field 318 can be omitted from the low-overheadbeacon frame 500 because sequence control may be unnecessary in abeacon.

In an embodiment, the frame control (FC) field 510 contains a flagindicating that the beacon frame 500 is a low-overhead beacon (LOB),also referred to as a “short beacon,” and more specifically a “TIM shortbeacon.” In an embodiment, the FC field 510 can indicate that the beaconframe 500 is a TIM short beacon by setting a “type value” (which can bebits B3:B2 of the FC field 510) to “11” (which can indicate a beaconframe) and by setting a “subtype value” (which can be bits B7:B4 of theFC field 510) to “0010” (which can indicate that the beacon iscompressed, low-overhead, “short,” and/or targeted at associated STAB).When a STA receives the beacon frame 500, it can decode the FC field 510containing the flag indicating that the beacon frame 500 is a TIM shortbeacon. Accordingly, the STA can decode the beacon frame 500 inaccordance with the format described herein. As discussed above, the STAreceiving the TIM short beacon may be associated with the APtransmitting the TIM short beacon.

In the illustrated embodiment of FIG. 5, the timestamp field 540 isshorter than the timestamp field 320 described above with respect toFIG. 3. Specifically, the timestamp field 540 is only four bytes long,whereas the timestamp field 320 is eight bytes long. In an embodiment, aSTA receiving the low-overhead beacon 500 can retrieve a completeeight-byte timestamp from a transmitting AP via a probe request. In oneembodiment, the length of the timestamp field 540 can be chosen suchthat the timestamp field 540 will not overflow more than once everyseven minutes. In a conventional system, the timestamp field 320 valueis interpreted as a number of nanoseconds. In an embodiment, thetimestamp field 540 value can be interpreted as a number of OFDM symbolperiods. Accordingly, in embodiments where an OFDM symbol period islonger than a nanosecond, the timestamp field 540 may not overflow asquickly.

In an embodiment, the timestamp field 540 can facilitate a timingsynchronization function (TSF) between devices 104 and 106 in thewireless communication system 100. In embodiments where the AP 104updates the timestamp field 540 at 1 MHz, a four-byte timestamp field540 will overflow approximately every 72 minutes. In embodiments wheredevice clocks drive at about +/−20 ppm, it would take approximately 1.4years to drive by 30 min. Accordingly, a device 106 can maintain timesynchronization with the AP 104 if it checks the beacon 500 as rarely asonce a day.

In the illustrated embodiment of FIG. 5, the change sequence field 550can serve to provide a sequence number indicative of a change in networkinformation. In the illustrated embodiment, the change sequence field550 serves keep track of changes to the AP 104. In an embodiment, the AP104 may increment the change sequence field 550 when one or moreparameters of the AP 104 change. For example, the AP may transmit a fullbeacon when the SSID changes. In one embodiment, the AP 104 maydecrement the change sequence field 550, change the change sequencefield 550 to a random or pseudorandom number, or otherwise modify thechange sequence field 550 when the configuration of the AP 104 changes.In various embodiments, the change sequence field 550 may be referred toas a beacon index or a beacon number.

The STA 106 can be configured to detect a change in the change sequencefield 550. When the STA 106 detects the change in the change sequencefield 550, the STA 106 may wait for the transmission of a full beacon.The STA 106 may delay transitioning to a sleep or low-power mode whileit waits for the AP 104 to transmit a full beacon. In anotherembodiment, the STA 106 may send a probe request frame to the AP 104when the STA 106 detects the change in the change sequence field 550.The AP 104 may send updated configuration information to the STA 106 inresponse to the probe request frame.

Referring still to FIG. 5, the TIM IE field 566 serves to identify whichstations using power saving mode have data frames waiting for them inthe access point's buffer. In an embodiment, the TIM IE field 566 can bea bitmap. The TIM IE field 566 can identify a station by an associationID (AID) that the access point assigns during the association process.

Referring still to FIG. 5, the CRC field 580 can serve a purpose similarto that of the FCS field 306 described above with respect to FIG. 3.Specifically, the CRC field 580 can allow a receiving STA to identifytransmission errors in a received beacon. Although the CRC field 580 isshown as four bytes long, the CRC field 580 can be different lengths invarious embodiments. In one embodiment, for example, the CRC field 580is two bytes long. In another embodiment, the CRC field 580 is one bytelong. The CRC field 580 can be another type of check code. In anembodiment, the CRC field 580 is a message integrity check (MIC).

FIG. 6 is a timing diagram 600 illustrating exemplary beacon timing. Asdiscussed herein, the AP 104 can be configured to transmit a “fullbeacon” and/or one or more “short beacons” at various intervals. In anembodiment, the AP 104 can transmit a short beacon 620 and 630 at eachbeacon interval 610. In various embodiments, the short beacon 620 and630 can include, for example, one or more of the low-overhead beaconframe 400 (FIG. 4) and the TIM short beacon 500 (FIG. 5). The beaconinterval 610 can be communicated, for example, in the beacon intervalfield 322 (FIG. 3). For example, in an embodiment, the beacon interval610 can be 100 TUs or 102400 ns.

Referring still to FIG. 6, the illustrated embodiment, the AP 104transmits the short beacon 620 and 630 only during beacon intervalsduring which it does not transmit a full beacon 640. The AP 104 cantransmit the full beacon 640 at a full beacon interval 650. In anembodiment, the full beacon 640 can include, for example, the fullbeacon 300 (FIG. 3). The full beacon interval 650 can be a firstmultiple of the beacon interval 610. For example, in the illustratedembodiment, the full beacon interval 650 is six times the beaconinterval 610. In various embodiments, the full beacon interval 650 canbe equal to the beacon interval 610, two times the beacon interval 610,three times the beacon interval 610, and so on.

Referring still to FIG. 6, in the illustrated embodiment, the AP 104 caninclude a traffic indication map (TIM) element in each beacontransmitted at a TIM period 660. The TIM period 660 can be a secondmultiple of the beacon interval 610. For example, in the illustratedembodiment, the TIM period 660 is twice the beacon interval 610. Invarious embodiments, the TIM period 660 can be equal to the beaconinterval 610, three times the beacon interval 610, four times the beaconinterval 610, and so on. As shown, the AP 104 includes the TIM in thefull beacons 640 and the short beacons 630, in accordance with a TIMperiod 660 of two beacon intervals 610. Similarly, in variousembodiments, the AP 104 can include a delivery traffic indication map(DTIM) element in each beacon transmitted at a DTIM period (not shown).

In an embodiment, the AP may not transmit the TIM short beacons 630.Instead, all short beacons 620 and 630 may be SSID short beacons 620.For example, the short beacons 620 and 630 can all be the low-overheadbeacon 400 (FIG. 4).

FIG. 7 shows a flowchart 700 of an exemplary method for generating acompressed, or low-overhead, beacon. The method of flowchart 700 may beused to create a low-overhead beacon such as, for example, thelow-overhead beacon 400 described above with respect to FIG. 4. Thecompressed beacon may be generated at the AP 104 (FIG. 1) andtransmitted to another node in the wireless communication system 100.Although the method is described below with respect to elements of thewireless device 202 a (FIG. 2), those having ordinary skill in the artwill appreciate that the method of flowchart 700 may be implemented byany other suitable device. In an embodiment, the steps in flowchart 700may be performed by the processor 204 in conjunction with thetransmitter 210 and the memory 206. Although the method of flowchart 700is described herein with reference to a particular order, in variousembodiments, blocks herein may be performed in a different order, oromitted, and additional blocks may be added.

First, at block 710, the wireless device 202 a creates a shortenednetwork identifier. The shortened network identifier can be shorter thana full network identifier. For example, the shortened network identifiercan be the compressed SSID 460 (FIG. 4), and the full network identifiercan be the SSID 326 (FIG. 3). In an embodiment, the processor 204creates a 1-byte SSID hash from the SSID of the AP 104. In anotherembodiment, the processor 204 can compute a 4-byte cyclic redundancycheck (CRC) on the full network identifier. The processor 204 can usethe same generator polynomial used to compute the CRC 490. In variousother embodiments, the processor 204 can shorten the SSID in anothermanner, such as, for example, truncation, cryptographic hashing, etc. Inanother embodiment, the wireless device 202 a can create a shortenedidentifier from an identifier other than the SSID. In one embodiment,for example, the wireless device 202 a can shorten a BSSID. The creationof the SSID hash may be performed by the processor 204 and/or the DSP220, for example.

Next, at block 720, the wireless device 202 a generates the compressedbeacon. The compressed beacon can include the SSID hash or anothershortened identifier, as discussed above with respect to block 710. Inan embodiment, the wireless device 202 a can generate the compressedbeacon in accordance with the compressed beacon frame 400 discussedabove with respect to FIG. 4. The generation may be performed by theprocessor 204 and/or the DSP 220, for example.

Thereafter, at block 730, the wireless device 202 a wirelessly transmitsthe compressed beacon. The transmission may be performed by thetransmitter 210, for example.

FIG. 8 is a functional block diagram of an exemplary wireless device 800that may be employed within the wireless communication system 100 ofFIG. 1. Those skilled in the art will appreciate that a wireless device800 may have more components than the simplified wireless device 800illustrated in FIG. 8. The illustrated wireless device 800 includes onlythose components useful for describing some prominent features ofimplementations within the scope of the claims. The device 800 includesmeans 810 for creating a shortened network identifier, means 820 forgenerating a compressed beacon including the shortened networkidentifier, and means 830 for transmitting the compressed beacon.

Means 810 for creating a shortened network identifier may be configuredto perform one or more of the functions discussed above with respect tothe block 710 illustrated in FIG. 7. Means 810 for creating a shortenednetwork identifier may correspond to one or more of the processor 204and the DSP 220 (FIG. 2). Means 820 for generating a compressed beaconincluding the shortened network identifier may be configured to performone or more of the functions discussed above with respect to the block720 illustrated in FIG. 7. Means 820 for generating a compressed beaconincluding the shortened network identifier may correspond to one or moreof the processor 204 and the DSP 220. Means 830 for transmitting thecompressed beacon may be configured to perform one or more of thefunctions discussed above with respect to the block 730 illustrated inFIG. 7. Means 830 for transmitting the compressed beacon may correspondto the transmitter 210.

FIG. 9 shows a flowchart 900 of an exemplary method for processing acompressed, or low-overhead, beacon. The method of flowchart 900 may beused to process a low-overhead beacon such as, for example, thelow-overhead beacon 400 described above with respect to FIG. 4. Thecompressed beacon may be processed at the STA 106 (FIG. 1) and receivedfrom another node in the wireless communication system 100. Although themethod is described below with respect to elements of the wirelessdevice 202 s (FIG. 2), those having ordinary skill in the art willappreciate that the method of flowchart 900 may be implemented by anyother suitable device. In an embodiment, the steps in flowchart 900 maybe performed by the processor 204 in conjunction with the receiver 212and the memory 206. Although the method of flowchart 900 is describedherein with reference to a particular order, in various embodiments,blocks herein may be performed in a different order, or omitted, andadditional blocks may be added.

First, at block 910, the wireless device 202 s receives a compressedbeacon including a shortened network identifier. The shortened networkidentifier can be shorter than a full network identifier. For example,the shortened network identifier can be the compressed SSID 460 (FIG.4), and the full network identifier can be the SSID 326 (FIG. 3). Thedevice 202 s may be associated with a network having a networkidentifier. For example, the device 202 s may be associated with thecommunication system 100 via the AP 104, which can have an SSID. Thecompressed beacon can be received via the receiver 212, for example.

Next, at block 920, the wireless device 202 s creates an expectedshortened network identifier based on the network identifier of thenetwork associated with the device 202 s. For example, the processor 204can compute and create a 1-byte SSID hash from the SSID of the AP 104.In another embodiment, the processor 204 can compute a 4-byte cyclicredundancy check (CRC) on the full network identifier. The processor 204can use the same generator polynomial used to compute the CRC 490. Invarious other embodiments, the processor 204 can shorten the SSID inanother manner, such as, for example, truncation, cryptographic hashing,etc. In another embodiment, the wireless device 202 s can create anexpected shortened identifier from an identifier other than the SSID. Inone embodiment, for example, the wireless device 202 s can shorten aBSSID. The creation of the expected shortened network identifier may beperformed by the processor 204 and/or the DSP 220, for example.

Then, at block 930, the wireless device 202 s compares the expectedshortened network identifier, generated using the SSID of the associatedAP 104, to the received shortened network identifier. The comparison maybe performed by the processor 204 and/or the DSP 220, for example.

Thereafter, at block 940, the wireless device 202 s discards thereceived compressed beacon when the received shortened networkidentifier does not match the expected shortened network identifier. Themismatch can indicate that the received compressed beacon is not from anassociated AP. The compressed beacon may be discarded by the processor204 and/or the DSP 220, for example.

Subsequently, at block 950, the wireless device 202 s processes thecompressed beacon when the received shortened network identifier matchesthe expected shortened network identifier. The match can indicate thatthe received compressed beacon is from an associated AP. The compressedbeacon may be processed by the processor 204 and/or the DSP 220, forexample.

FIG. 10 is a functional block diagram of another exemplary wirelessdevice 1000 that may be employed within the wireless communicationsystem 100 of FIG. 1. Those skilled in the art will appreciate that awireless device 1000 may have more components than the simplifiedwireless device 1000 illustrated in FIG. 10. The illustrated wirelessdevice 1000 includes only those components useful for describing someprominent features of implementations within the scope of the claims.The device 1000 includes means 1010 for receiving, at an apparatusassociated with a network having a network identifier, a compressedbeacon including a shortened network identifier, means 1020 for creatingan expected shortened network identifier based on the network identifierof the network associated with the apparatus, means 1030 for comparingthe expected shortened network identifier to the received shortenednetwork identifier, means 1040 for discarding the compressed beacon whenthe expected shortened network identifier does not match the receivedshortened network identifier, and means 1050 for processing thecompressed beacon when the expected shortened network identifier doesnot match the received shortened network identifier.

Means 1010 for receiving, at an apparatus associated with a networkhaving a network identifier, a compressed beacon including a shortenednetwork identifier may be configured to perform one or more of thefunctions discussed above with respect to the block 910 illustrated inFIG. 9. Means 1010 for receiving, at an apparatus associated with anetwork having a network identifier, a compressed beacon including ashortened network identifier may correspond to one or more of thereceiver 212 and the memory 206 (FIG. 2).

Means 1020 for creating an expected shortened network identifier basedon the network identifier of the network associated with the apparatusmay be configured to perform one or more of the functions discussedabove with respect to the block 920 illustrated in FIG. 9. Means 1020for creating an expected shortened network identifier based on thenetwork identifier of the network associated with the apparatus maycorrespond to one or more of the processor 204 and the DSP 220.

Means 1030 for comparing the expected shortened network identifier tothe received shortened network identifier may be configured to performone or more of the functions discussed above with respect to the block930 illustrated in FIG. 9. Means 1030 for comparing the expectedshortened network identifier to the received shortened networkidentifier may correspond to one or more of the processor 204 and theDSP 220.

Means 1040 for discarding the compressed beacon when the expectedshortened network identifier does not match the received shortenednetwork identifier may be configured to perform one or more of thefunctions discussed above with respect to the block 940 illustrated inFIG. 9. Means 1040 for discarding the compressed beacon when theexpected shortened network identifier does not match the receivedshortened network identifier may correspond to one or more of theprocessor 204 and the DSP 220.

Means 1050 for processing the compressed beacon when the expectedshortened network identifier does not match the received shortenednetwork identifier may be configured to perform one or more of thefunctions discussed above with respect to the block 950 illustrated inFIG. 9. Means 1050 for processing the compressed beacon when theexpected shortened network identifier does not match the receivedshortened network identifier may correspond to one or more of theprocessor 204 and the DSP 220.

FIG. 11 shows a flowchart 1100 of another exemplary method forgenerating a compressed, or low-overhead, beacon. The method offlowchart 1100 may be used to create a low-overhead beacon such as, forexample, the low-overhead beacon 400 described above with respect toFIG. 4. The compressed beacon may be generated at the AP 104 (FIG. 1)and transmitted to another node in the wireless communication system100. Although the method is described below with respect to elements ofthe wireless device 202 a (FIG. 2), those having ordinary skill in theart will appreciate that the method of flowchart 1100 may be implementedby any other suitable device. In an embodiment, the steps in flowchart1100 may be performed by the processor 204 in conjunction with thetransmitter 210 and the memory 206. Although the method of flowchart1100 is described herein with reference to a particular order, invarious embodiments, blocks herein may be performed in a differentorder, or omitted, and additional blocks may be added.

First, at block 1110, the wireless device 202 a generates a compressedbeacon including a next full beacon time indication. In an embodiment,the next full beacon time indication can be the next full beacon timeindication field 450, described above with respect to FIG. 4. Thewireless device 202 a can determine the next time it will transmit afull beacon, such as the beacon 300 (FIG. 3). This time can be referredto as the next target beacon transmit time (TBTT). In an embodiment, thenext full beacon time indication can include the time at which theaccess point will transmit a full beacon. The next full beacon timeindication can be the 3 most significant bytes, of the 4 leastsignificant bytes of a next target beacon transmit time (TBTT).

In another embodiment, the next full beacon time indication can includea flag indicating that the wireless device 202 a will transmit a fullbeacon including one or more fields not included in the compressedbeacon. The flag may indicate that the next beacon transmitted will be afull beacon. In another embodiment, the next full beacon time indicationcan include a value indicating a duration until the wireless device 202a transmits the next full beacon. The next full beacon time indicationcan indicate the number of time units (TUs) until the access pointtransmits the next full beacon. The compressed beacon and next fullbeacon time indication can be generated by the processor 204 and/or theDSP 220, for example.

Next, at block 1120, the wireless device 202 a wirelessly transmits thecompressed beacon. The transmission may be performed by the transmitter210, for example. Thereafter, at the next TBTT, the wireless device 202a can generate and transmit the full beacon and transmit.

FIG. 12 is a functional block diagram of another exemplary wirelessdevice 1200 that may be employed within the wireless communicationsystem 100 of FIG. 1. Those skilled in the art will appreciate that awireless device 1200 may have more components than the simplifiedwireless device 1200 illustrated in FIG. 12. The illustrated wirelessdevice 1200 includes only those components useful for describing someprominent features of implementations within the scope of the claims.The device 1200 includes means 1210 for generating a compressed beaconincluding a next full beacon time indication, and means 1220 fortransmitting the compressed beacon.

Means 1210 for generating a compressed beacon including a next fullbeacon time indication may be configured to perform one or more of thefunctions discussed above with respect to the block 1110 illustrated inFIG. 11. Means 1210 for generating a compressed beacon including a nextfull beacon time indication may correspond to one or more of theprocessor 204 and the DSP 220 (FIG. 2). Means 1220 for transmitting thecompressed beacon may be configured to perform one or more of thefunctions discussed above with respect to the block 1120 illustrated inFIG. 11. Means 1220 for transmitting the compressed beacon maycorrespond to the transmitter 210.

FIG. 13 shows a flowchart 1300 of an exemplary method for operating thewireless device 202 s of FIG. 2. Although the method is described belowwith respect to elements of the wireless device 202 s (FIG. 2), thosehaving ordinary skill in the art will appreciate that the method offlowchart 1300 may be implemented by any other suitable device. In anembodiment, the steps in flowchart 1300 may be performed by theprocessor 204 in conjunction with the receiver 212, the power supply230, and the memory 206. Although the method of flowchart 1300 isdescribed herein with reference to a particular order, in variousembodiments, blocks herein may be performed in a different order, oromitted, and additional blocks may be added.

First, at block 1310, the wireless device 202 s receives a compressedbeacon including a next full beacon time indication (NFBTI). Thecompressed beacon can be, for example, the low-overhead beacon 400described above with respect to FIG. 4. The compressed beacon may begenerated at the AP 104 (FIG. 1) and transmitted to the STA 106 via thewireless communication system 100. The wireless device 202 s can receivethe compressed beacon using the receiver 212, for example.

In an embodiment, the next full beacon time indication can be the nextfull beacon time indication field 450, described above with respect toFIG. 4. As discussed above, the wireless device 202 a can determine thenext time it will transmit a full beacon, such as the beacon 300 (FIG.3). This time can be referred to as the next target beacon transmit time(TBTT). In an embodiment, the next full beacon time indication caninclude the time at which the access point will transmit a full beacon.The next full beacon time indication can be the 3 most significantbytes, of the 4 least significant bytes of a next target beacon transmittime (TBTT).

In another embodiment, the next full beacon time indication can includea flag indicating that the wireless device 202 a will transmit a fullbeacon including one or more fields not included in the compressedbeacon. The flag may indicate that the next beacon transmitted will be afull beacon. In another embodiment, the next full beacon time indicationcan include a value indicating a duration until the wireless device 202a transmits the next full beacon. The next full beacon time indicationcan indicate the number of time units (TUs) until the access pointtransmits the next full beacon.

Next, at block 1320, the wireless device 202 s operates in a first powermode for a duration based on the next full beacon time indication. Forexample, the wireless device 202 s may enter a low power state untilshortly before the next full beacon will be transmitted in order to savepower. For example, the wireless device 202 s may shut down, or placeinto a low power mode, one or more components such as the processor 204,the transmitter 210, and/or the receiver 212.

The wireless device 202 s may determine the next time that the AP 104will transmit the full beacon based on the next full beacon timeindication received in the compressed beacon. The processor 204 may seta timer to wake up at least a first time before the next full beacon isexpected. The wireless device 202 s may operate in the first power modevia the power supply 230, in conjunction with other components.

Then, at block 1330, the wireless device 202 s transitions to a second,lower power mode at the end of the duration. For example, at theexpiration of a timer, the wireless device 204 may wake up from a lowpower mode and active, or put into a higher-power mode, one or more ofthe processor 204, the transmitter 210, and the receiver 212. Thewireless device 202 s may transition into the second power mode via thepower supply 230, in conjunction with other components. Subsequently,the wireless device 202 s may receive the full beacon from the AP 104.

FIG. 14 is a functional block diagram of another exemplary wirelessdevice 1400 that may be employed within the wireless communicationsystem 100 of FIG. 1. Those skilled in the art will appreciate that awireless device 1400 may have more components than the simplifiedwireless device 1400 illustrated in FIG. 14. The illustrated wirelessdevice 1400 includes only those components useful for describing someprominent features of implementations within the scope of the claims.The device 1400 includes means 1410 for receiving a compressed beaconincluding a next full beacon time indication (NFBTI), means 1420 foroperating a wireless device in a first power mode for a duration basedon the next full beacon time indication, and means 1430 transitioningthe wireless device to a second, higher power mode at the end of theduration.

Means 1410 for receiving a compressed beacon including a next fullbeacon time indication may be configured to perform one or more of thefunctions discussed above with respect to the block 1310 illustrated inFIG. 13. Means 1410 for receiving a compressed beacon including a nextfull beacon time indication may correspond to one or more of theprocessor 204 and the receiver 212 (FIG. 2). Means 1420 for operating awireless device in a first power mode for a duration based on the nextfull beacon time indication may be configured to perform one or more ofthe functions discussed above with respect to the block 1320 illustratedin FIG. 13. Means 1420 for operating a wireless device in a first powermode for a duration based on the next full beacon time indication maycorrespond to one or more of the processor 204 and the power supply 230.Means 1430 transitioning the wireless device to a second, higher powermode at the end of the duration may be configured to perform one or moreof the functions discussed above with respect to the block 1330illustrated in FIG. 13. Means 1430 transitioning the wireless device toa second, higher power mode at the end of the duration may correspond toone or more of the processor 204 and the power supply 230.

FIG. 15 shows a flowchart 1500 of an exemplary method for communicatingin the wireless communication system 100 of FIG. 1. The method offlowchart 1500 may be used to create and transmit a low-overhead beaconsuch as, for example, the low-overhead beacon 400 described above withrespect to FIG. 4. The compressed beacon may be generated at the AP 104(FIG. 1) and transmitted to another node in the wireless communicationsystem 100. Although the method is described below with respect toelements of the wireless device 202 a (FIG. 2), those having ordinaryskill in the art will appreciate that the method of flowchart 1500 maybe implemented by any other suitable device. In an embodiment, the stepsin flowchart 1500 may be performed by the processor 204 in conjunctionwith the transmitter 210 and the memory 206. Although the method offlowchart 1500 is described herein with reference to a particular order,in various embodiments, blocks herein may be performed in a differentorder, or omitted, and additional blocks may be added.

First, at block 1510, the wireless device 202 a transmits a full beaconat a first multiple of a beacon interval. In an embodiment, the fullbeacon can be the beacon 300 described above with respect to FIG. 3. Invarious embodiments, the first multiple can be 2, 3, 4, 5, etc. Thewireless device 202 a can communicate the beacon interval and/or thefirst multiple to a STA 106 via a field in the full beacon, in responseto a probe request, or it may be preset. The wireless device 202 a cangenerate the full beacon using the processor 204, and can transmit thefull beacon via the transmitter 210, for example.

Next, at block 1520, at block 1510, the wireless device 202 a transmitsa compressed beacon at each beacon interval that is not the firstmultiple of the beacon interval. The compressed beacon can be, forexample, the beacon 400 (FIG. 4). In one embodiment, the wireless device202 a can transmit the compressed beacon at a second multiple of thebeacon interval, except where the second multiple coincides with thefirst multiple. The wireless device 202 a can generate the compressedbeacon using the processor 204, and can transmit the compressed beaconvia the transmitter 210, for example.

FIG. 16 is a functional block diagram of another exemplary wirelessdevice 1600 that may be employed within the wireless communicationsystem 100 of FIG. 1. Those skilled in the art will appreciate that awireless device 1600 may have more components than the simplifiedwireless device 1600 illustrated in FIG. 16. The illustrated wirelessdevice 1600 includes only those components useful for describing someprominent features of implementations within the scope of the claims.The device 1600 includes means 1610 for transmitting a full beacon at afirst multiple of a beacon interval, and means 1620 for transmitting acompressed beacon at each beacon interval that is not the first multipleof the beacon interval.

Means 1610 for transmitting a full beacon at a first multiple of abeacon interval may be configured to perform one or more of thefunctions discussed above with respect to the block 1510 illustrated inFIG. 15. Means 1610 for transmitting a full beacon at a first multipleof a beacon interval may correspond to one or more of the processor 204and the transmitter 210 (FIG. 2). Means 1620 for transmitting acompressed beacon at each beacon interval that is not the first multipleof the beacon interval may be configured to perform one or more of thefunctions discussed above with respect to the block 1520 illustrated inFIG. 15. Means 1620 for transmitting a compressed beacon at each beaconinterval that is not the first multiple of the beacon interval maycorrespond to one or more of the processor 204 and the transmitter 210(FIG. 2).

FIG. 17 shows a flowchart 1700 of another exemplary method forcommunicating in the wireless communication system 100 of FIG. 1. Themethod of flowchart 1700 may be used to receive a low-overhead beaconsuch as, for example, the low-overhead beacon 400 described above withrespect to FIG. 4. The compressed beacon may be generated at the AP 104(FIG. 1) and transmitted to a STA 106 in the wireless communicationsystem 100. Although the method is described below with respect toelements of the wireless device 202 s (FIG. 2), those having ordinaryskill in the art will appreciate that the method of flowchart 1700 maybe implemented by any other suitable device. In an embodiment, the stepsin flowchart 1700 may be performed by the processor 204 in conjunctionwith the transmitter 210 and the memory 206. Although the method offlowchart 1700 is described herein with reference to a particular order,in various embodiments, blocks herein may be performed in a differentorder, or omitted, and additional blocks may be added.

First, at block 1710, the wireless device 202 s receives a full beaconat a first multiple of a beacon interval. In an embodiment, the fullbeacon can be the beacon 300 described above with respect to FIG. 3. Invarious embodiments, the first multiple can be 2, 3, 4, 5, etc. Thewireless device 202 s can receive the beacon interval and/or the firstmultiple from the AP 104 via a field in the full beacon, in response toa probe request, or it may be preset. The wireless device 202 s canreceive the full beacon via the receiver 212, for example.

Next, at block 1720, at block 1710, the wireless device 202 s receives acompressed beacon at a beacon interval that is not the first multiple ofthe beacon interval. The compressed beacon can be, for example, thebeacon 400 (FIG. 4). In one embodiment, the wireless device 202 s canreceive the compressed beacon at a second multiple of the beaconinterval, except where the second multiple coincides with the firstmultiple. The wireless device 202 s can receive via the receiver 212,for example.

FIG. 18 is a functional block diagram of another exemplary wirelessdevice 1800 that may be employed within the wireless communicationsystem 100 of FIG. 1. Those skilled in the art will appreciate that awireless device 1800 may have more components than the simplifiedwireless device 1800 illustrated in FIG. 18. The illustrated wirelessdevice 1800 includes only those components useful for describing someprominent features of implementations within the scope of the claims.The device 1800 includes means 1810 for receiving a full beacon at afirst multiple of a beacon interval, and means 1820 for receiving acompressed beacon at a beacon interval that is not the first multiple ofthe beacon interval.

Means 1810 for receiving a full beacon at a first multiple of a beaconinterval may be configured to perform one or more of the functionsdiscussed above with respect to the block 1710 illustrated in FIG. 17.Means 1810 transmitting a full beacon at a first multiple of a beaconinterval may correspond to one or more of the processor 204 and thereceiver 212 (FIG. 2). Means 1820 for receiving a compressed beacon at abeacon interval that is not the first multiple of the beacon intervalmay be configured to perform one or more of the functions discussedabove with respect to the block 1720 illustrated in FIG. 17. Means 1820for receiving a compressed beacon at each beacon interval that is notthe first multiple of the beacon interval may correspond to one or moreof the processor 204 and the receiver 212 (FIG. 2).

Several embodiments described above include a compressed SSID field(e.g., 460). In some implementations, the compressed SSID field may beselectively generated. In some implementations, the selection may bebased on the length of the full SSID for the signal. For example, if thelength of the full SSID (e.g., four bytes) is equal to the length of thecompressed SSID field (e.g., four bytes), the full SSID may be used asthe compressed SSID. In some implementations, if the length of full SSIDis longer than the length of the compressed SSID field, a CRC computedon a portion of, or all of the full SSID, may be used as the compressedSSID. The computed CRC may have a length equal to the length of thecompressed SSID field. In some implementations, if the length of thefull SSID is less than the length of the compressed SSID field, the fullSSID may be increased in length (e.g., padded) to equal the length ofthe compressed SSID field to form the compressed SSID. For example, ifthe compressed SSID field is eight bytes and the full SSID is fourbytes, four bytes of padding may be added to the full SSID to generatean eight byte compressed SSID. The padding may be included before thefull SSID (e.g., at the beginning) or after the full SSID (e.g., at theend). The padding may include a null character, a padding character(e.g., alphanumeric, non-alphanumeric), or a combination thereof.

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like. Further, a “channel width” as used herein may encompass ormay also be referred to as a bandwidth in certain aspects.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover: a, b, c,a-b, a-c, b-c, and a-b-c.

The various operations of methods described above may be performed byany suitable means capable of performing the operations, such as varioushardware and/or software component(s), circuits, and/or module(s).Generally, any operations illustrated in the Figures may be performed bycorresponding functional means capable of performing the operations.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array signal (FPGA) or other programmable logic device(PLD), discrete gate or transistor logic, discrete hardware componentsor any combination thereof designed to perform the functions describedherein. A general purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

In one or more aspects, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored on or transmitted over as oneor more instructions or code on a computer-readable medium.Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage media may be anyavailable media that can be accessed by a computer. By way of example,and not limitation, such computer-readable media can include RAM, ROM,EEPROM, CD-ROM or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other medium that can be used tocarry or store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Thus, in some aspects computer readable medium may includenon-transitory computer readable medium (e.g., tangible media). Inaddition, in some aspects computer readable medium may includetransitory computer readable medium (e.g., a signal). Combinations ofthe above should also be included within the scope of computer-readablemedia.

The methods disclosed herein include one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

The functions described may be implemented in hardware, software,firmware or any combination thereof. If implemented in software, thefunctions may be stored as one or more instructions on acomputer-readable medium. A storage media may be any available mediathat can be accessed by a computer. By way of example, and notlimitation, such computer-readable media can include RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers.

Thus, certain aspects may include a computer program product forperforming the operations presented herein. For example, such a computerprogram product may include a computer readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein. For certain aspects, the computer program product may includepackaging material.

Software or instructions may also be transmitted over a transmissionmedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition oftransmission medium.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

While the foregoing is directed to aspects of the present disclosure,other and further aspects of the disclosure may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method of communicating in a wireless network, comprising:generating a compressed beacon comprising: a next full beacon timeindication (NFBTI); and transmitting, at an access point, the compressedbeacon.
 2. The method of claim 1, wherein the next full beacon timeindication comprises a time at which the access point will transmit afull beacon comprising one or more fields not included in the compressedbeacon.
 3. The method of claim 2, wherein the next full beacon timeindication comprises the 3 most significant bytes, of the 4 leastsignificant bytes of a next target beacon transmit time (TBTT).
 4. Themethod of claim 1, wherein the next full beacon time indicationcomprises a flag indicating that the access point will transmit a fullbeacon comprising one or more fields not included in the compressedbeacon.
 5. The method of claim 4, further comprising: generating thefull beacon; and transmitting the full beacon.
 6. The method of claim 1,wherein the next full beacon time indication comprises a valueindicating a duration until the access point transmits the next fullbeacon.
 7. The method of claim 6, wherein the next full beacon timeindication indicates the number of time units (TUs) until the accesspoint transmits the next full beacon.
 8. The method of claim 7, whereinthe next full beacon time indication comprises a null value when numberof beacon intervals to the next full beacon is not determined.
 9. Themethod of claim 1, wherein the compressed beacon comprises: a framecontrol field; a source address; a timestamp; a change sequence; thenext full beacon time indication; and a frame check.
 10. The method ofclaim 9, wherein the frame control field comprises 2 bytes, the sourceaddress comprises 6 bytes, the timestamp comprises 4 bytes, the changesequence comprises 1 byte, the next full beacon time indicationcomprises 3 bytes, and the frame check comprises 4 bytes.
 11. The methodof claim 9, wherein the source address comprises a basic service setidentification (BSSID) of the access point.
 12. The method of claim 9,wherein the timestamp comprises a shortened timestamp comprising fewerbits than a full timestamp.
 13. The method of claim 12, wherein thetimestamp comprises a one or more least significant bits of the fulltimestamp.
 14. The method of claim 9, the method further comprisingchanging the change sequence when an access point or networkconfiguration changes or when there is a substantial change in thecontent of a full beacon.
 15. The method of claim 9, wherein the framecontrol field comprises a version field, a type field, a subtype field,a next full beacon time indication (NFBTI) present field, a service setidentifier (SSID) present field, an internetworking present field, abandwidth field, a security field, and one or more reserved bits. 16.The method of claim 15, wherein the version field comprises 2 bits, thetype field comprises 2 bits, the subtype field comprises 4 bits, theNFBTI present field comprises 1 bit, the SSID present flag comprises 1bit, the internetworking present field comprises 1 bit, the bandwidthfield comprises 3 bits, the security field comprises 1 bit, and the oneor more reserved bits comprise 1 bit.
 17. The method of claim 15,wherein type field comprises a value of “11” and the subtype fieldcomprises a value of “0001,” indicating that the beacon is a compressedbeacon.
 18. A method of communicating in a wireless network, comprising:receiving, at a wireless device, a compressed beacon comprising a nextfull beacon time indication (NFBTI); operating the wireless device in afirst power mode for a duration based on the next full beacon timeindication; and transitioning the wireless device to a second power modeat the end of the duration, wherein the wireless device consumes a firstpower when in the first power mode, and a second power when in thesecond power mode, the first power being lower than the second power.19. The method of claim 18, wherein the next full beacon time indicationcomprises a time at which the access point will transmit a full beaconcomprising one or more fields not included in the compressed beacon. 20.The method of claim 19, wherein the next full beacon time indicationcomprises the 3 most significant bytes, of the 4 least significant bytesof a next target beacon transmit time (TBTT).
 21. The method of claim18, wherein the next full beacon time indication comprises a flagindicating that the access point will transmit a full beacon comprisingone or more fields not included in the compressed beacon.
 22. The methodof claim 21, further comprising receiving the full beacon aftertransitioning the wireless device to the second power mode.
 23. Themethod of claim 18, wherein the next full beacon time indicationcomprises a value indicating a duration until the access point transmitsthe next full beacon.
 24. The method of claim 23, wherein the next fullbeacon time indication indicates the number of time units (TUs) untilthe access point transmits the next full beacon.
 25. The method of claim24, wherein the next full beacon time indication comprises a null valuewhen number of beacon intervals to the next full beacon is notdetermined.
 26. The method of claim 18, wherein the compressed beaconcomprises: a frame control field; a source address; a timestamp; achange sequence; the next full beacon time indication; and a framecheck.
 27. The method of claim 26, wherein the frame control fieldcomprises 2 bytes, the source address comprises 6 bytes, the timestampcomprises 4 bytes, the change sequence comprises 1 byte, the next fullbeacon time indication comprises 3 bytes, and the frame check comprises4 bytes.
 28. The method of claim 26, wherein the source addresscomprises a basic service set identification (BSSID) of the accesspoint.
 29. The method of claim 26, wherein the timestamp comprises ashortened timestamp comprising fewer bits than a full timestamp.
 30. Themethod of claim 29, wherein the timestamp comprises a one or more leastsignificant bits of the full timestamp.
 31. The method of claim 26, themethod further comprising: detecting a change in the change sequence;transmitting a probe request when a change in the change sequence isdetected; and receiving a probe response in response to the proberequest.
 32. The method of claim 26, wherein the frame control fieldcomprises a version field, a type field, a subtype field, a next fullbeacon time indication (NFBTI) present field, a service set identifier(SSID) present field, an internetworking present field, a bandwidthfield, a security field, and one or more reserved bits.
 33. The methodof claim 32, wherein the version field comprises 2 bits, the type fieldcomprises 2 bits, the subtype field comprises 4 bits, the NFBTI presentfield comprises 1 bit, the SSID present flag comprises 1 bit, theinternetworking present field comprises 1 bit, the bandwidth fieldcomprises 3 bits, the security field comprises 1 bit, and the one ormore reserved bits comprise 1 bit.
 34. The method of claim 32, whereintype field comprises a value of “11” and the subtype field comprises avalue of “0001,” indicating that the beacon is a compressed beacon. 35.A wireless device configured to communicate in a wireless network,comprising: a processor configured to generate a compressed beacon, thecompressed beacon comprising: a next full beacon time indication(NFBTI); and a transmitter configured to transmit the compressed beacon.36. The wireless device of claim 35, wherein the next full beacon timeindication comprises a time at which the access point will transmit afull beacon comprising one or more fields not included in the compressedbeacon.
 37. The wireless device of claim 36, wherein the next fullbeacon time indication comprises the 3 most significant bytes, of the 4least significant bytes of a next target beacon transmit time (TBTT).38. The wireless device of claim 35, wherein the next full beacon timeindication comprises a flag indicating that the access point willtransmit a full beacon comprising one or more fields not included in thecompressed beacon.
 39. The wireless device of claim 38, wherein: theprocessor is further configured to generate the full beacon, and thetransmitter is further configured to transmit the full beacon.
 40. Thewireless device of claim 35, wherein the next full beacon timeindication comprises a value indicating a duration until the accesspoint transmits the next full beacon.
 41. The wireless device of claim40, wherein the next full beacon time indication indicates the number oftime units (TUs) until the access point transmits the next full beacon.42. The wireless device of claim 41, wherein the next full beacon timeindication comprises a null value when number of beacon intervals to thenext full beacon is not determined.
 43. The wireless device of claim 35,wherein the compressed beacon comprises: a frame control field; a sourceaddress; a timestamp; a change sequence; the next full beacon timeindication; and a frame check.
 44. The wireless device of claim 43,wherein the frame control field comprises 2 bytes, the source addresscomprises 6 bytes, the timestamp comprises 4 bytes, the change sequencecomprises 1 byte, the next full beacon time indication comprises 3bytes, and the frame check comprises 4 bytes.
 45. The wireless device ofclaim 43, wherein the source address comprises a basic service setidentification (BSSID) of the access point.
 46. The wireless device ofclaim 43, wherein the timestamp comprises a shortened timestampcomprising fewer bits than a full timestamp.
 47. The wireless device ofclaim 46, wherein the timestamp comprises a one or more leastsignificant bits of the full timestamp.
 48. The wireless device of claim43, wherein the processor is further configured to change the changesequence when an access point or network configuration changes or whenthere is a substantial change in the content of a full beacon.
 49. Thewireless device of claim 43, wherein the frame control field comprises aversion field, a type field, a subtype field, a next full beacon timeindication (NFBTI) present field, a service set identifier (SSID)present field, an internetworking present field, a bandwidth field, asecurity field, and one or more reserved bits.
 50. The wireless deviceof claim 49, wherein the version field comprises 2 bits, the type fieldcomprises 2 bits, the subtype field comprises 4 bits, the NFBTI presentfield comprises 1 bit, the SSID present flag comprises 1 bit, theinternetworking present field comprises 1 bit, the bandwidth fieldcomprises 3 bits, the security field comprises 1 bit, and the one ormore reserved bits comprise 1 bit.
 51. The wireless device of claim 49,wherein type field comprises a value of “11” and the subtype fieldcomprises a value of “0001,” indicating that the beacon is a compressedbeacon.
 52. A wireless device configured to communicate in a wirelessnetwork, comprising: a receiver configured to receive a compressedbeacon comprising a next full beacon time indication (NFBTI); and aprocessor configured to: operate the wireless device in a first powermode for a duration based on the next full beacon time indication; andtransition the wireless device to a second power mode at the end of theduration, wherein the wireless device consumes a first power when in thefirst power mode, and a second power when in the second power mode, thefirst power being lower than the second power.
 53. The wireless deviceof claim 52, wherein the next full beacon time indication comprises atime at which the access point will transmit a full beacon comprisingone or more fields not included in the compressed beacon.
 54. Thewireless device of claim 53, wherein the next full beacon timeindication comprises the 3 most significant bytes, of the 4 leastsignificant bytes of a next target beacon transmit time (TBTT).
 55. Thewireless device of claim 52, wherein the next full beacon timeindication comprises a flag indicating that the access point willtransmit a full beacon comprising one or more fields not included in thecompressed beacon.
 56. The wireless device of claim 55, the receiver isfurther configured to receive the full beacon after the processortransitions the wireless device to the second power mode.
 57. Thewireless device of claim 52, wherein the next full beacon timeindication comprises a value indicating a duration until the accesspoint transmits the next full beacon.
 58. The wireless device of claim57, wherein the next full beacon time indication indicates the number oftime units (TUs) until the access point transmits the next full beacon.59. The wireless device of claim 58, wherein the next full beacon timeindication comprises a null value when number of beacon intervals to thenext full beacon is not determined.
 60. The wireless device of claim 52,wherein the compressed beacon comprises: a frame control field; a sourceaddress; a timestamp; a change sequence; the next full beacon timeindication; and a frame check.
 61. The wireless device of claim 60,wherein the frame control field comprises 2 bytes, the source addresscomprises 6 bytes, the timestamp comprises 4 bytes, the change sequencecomprises 1 byte, the next full beacon time indication comprises 3bytes, and the frame check comprises 4 bytes.
 62. The wireless device ofclaim 60, wherein the source address comprises a basic service setidentification (BSSID) of the access point.
 63. The wireless device ofclaim 60, wherein the timestamp comprises a shortened timestampcomprising fewer bits than a full timestamp.
 64. The wireless device ofclaim 63, wherein the timestamp comprises a one or more leastsignificant bits of the full timestamp.
 65. The wireless device of claim60, wherein: the processor is further configured to detect a change inthe change sequence; the transmitter is further configured to transmit aprobe request when a change in the change sequence is detected; and thereceiver is further configured to receive a probe response in responseto the probe request.
 66. The wireless device of claim 60, wherein theframe control field comprises a version field, a type field, a subtypefield, a next full beacon time indication (NFBTI) present field, aservice set identifier (SSID) present field, an internetworking presentfield, a bandwidth field, a security field, and one or more reservedbits.
 67. The wireless device of claim 66, wherein the version fieldcomprises 2 bits, the type field comprises 2 bits, the subtype fieldcomprises 4 bits, the NFBTI present field comprises 1 bit, the SSIDpresent flag comprises 1 bit, the internetworking present fieldcomprises 1 bit, the bandwidth field comprises 3 bits, the securityfield comprises 1 bit, and the one or more reserved bits comprise 1 bit.68. The wireless device of claim 66, wherein type field comprises avalue of “11” and the subtype field comprises a value of “0001,”indicating that the beacon is a compressed beacon.
 69. An apparatus forcommunicating in a wireless network, comprising: means for generating acompressed beacon comprising: a next full beacon time indication(NFBTI); and means for transmitting the compressed beacon.
 70. Theapparatus of claim 69, wherein the next full beacon time indicationcomprises a time at which the access point will transmit a full beaconcomprising one or more fields not included in the compressed beacon. 71.The apparatus of claim 70, wherein the next full beacon time indicationcomprises the 3 most significant bytes, of the 4 least significant bytesof a next target beacon transmit time (TBTT).
 72. The apparatus of claim69, wherein the next full beacon time indication comprises a flagindicating that the access point will transmit a full beacon comprisingone or more fields not included in the compressed beacon.
 73. Theapparatus of claim 72, further comprising: means for generating the fullbeacon; and means for transmitting the full beacon.
 74. The apparatus ofclaim 69, wherein the next full beacon time indication comprises a valueindicating a duration until the access point transmits the next fullbeacon.
 75. The apparatus of claim 74, wherein the next full beacon timeindication indicates the number of time units (TUs) until the accesspoint transmits the next full beacon.
 76. The apparatus of claim 75,wherein the next full beacon time indication comprises a null value whennumber of beacon intervals to the next full beacon is not determined.77. The apparatus of claim 69, wherein the compressed beacon comprises:a frame control field; a source address; a timestamp; a change sequence;the next full beacon time indication; and a frame check.
 78. Theapparatus of claim 77, wherein the frame control field comprises 2bytes, the source address comprises 6 bytes, the timestamp comprises 4bytes, the change sequence comprises 1 byte, the next full beacon timeindication comprises 3 bytes, and the frame check comprises 4 bytes. 79.The apparatus of claim 77, wherein the source address comprises a basicservice set identification (BSSID) of the access point.
 80. Theapparatus of claim 77, wherein the timestamp comprises a shortenedtimestamp comprising fewer bits than a full timestamp.
 81. The apparatusof claim 80, wherein the timestamp comprises a one or more leastsignificant bits of the full timestamp.
 82. The apparatus of claim 77,further comprising means for changing the change sequence when an accesspoint or network configuration changes or when there is a substantialchange in the content of a full beacon.
 83. The apparatus of claim 77,wherein the frame control field comprises a version field, a type field,a subtype field, a next full beacon time indication (NFBTI) presentfield, a service set identifier (SSID) present field, an internetworkingpresent field, a bandwidth field, a security field, and one or morereserved bits.
 84. The apparatus of claim 83, wherein the version fieldcomprises 2 bits, the type field comprises 2 bits, the subtype fieldcomprises 4 bits, the NFBTI present field comprises 1 bit, the SSIDpresent flag comprises 1 bit, the internetworking present fieldcomprises 1 bit, the bandwidth field comprises 3 bits, the securityfield comprises 1 bit, and the one or more reserved bits comprise 1 bit.85. The apparatus of claim 83, wherein type field comprises a value of“11” and the subtype field comprises a value of “0001,” indicating thatthe beacon is a compressed beacon.
 86. An apparatus for communicating ina wireless network, comprising: means for receiving a compressed beaconcomprising a next full beacon time indication (NFBTI); means foroperating a wireless device in a first power mode for a duration basedon the next full beacon time indication; and means for transitioning thewireless device to a second power mode at the end of the duration,wherein the wireless device consumes a first power when in the firstpower mode, and a second power when in the second power mode, the firstpower being lower than the second power.
 87. The apparatus of claim 86,wherein the next full beacon time indication comprises a time at whichthe access point will transmit a full beacon comprising one or morefields not included in the compressed beacon.
 88. The apparatus of claim87, wherein the next full beacon time indication comprises the 3 mostsignificant bytes, of the 4 least significant bytes of a next targetbeacon transmit time (TBTT).
 89. The apparatus of claim 86, wherein thenext full beacon time indication comprises a flag indicating that theaccess point will transmit a full beacon comprising one or more fieldsnot included in the compressed beacon.
 90. The apparatus of claim 89,further comprising means for receiving the full beacon aftertransitioning the wireless device to the second power mode.
 91. Theapparatus of claim 86, wherein the next full beacon time indicationcomprises a value indicating a duration until the access point transmitsthe next full beacon.
 92. The apparatus of claim 23, wherein the nextfull beacon time indication indicates the number of time units (TUs)until the access point transmits the next full beacon.
 93. The apparatusof claim 92, wherein the next full beacon time indication comprises anull value when number of beacon intervals to the next full beacon isnot determined.
 94. The apparatus of claim 86, wherein the compressedbeacon comprises: a frame control field; a source address; a timestamp;a change sequence; the next full beacon time indication; and a framecheck.
 95. The apparatus of claim 94, wherein the frame control fieldcomprises 2 bytes, the source address comprises 6 bytes, the timestampcomprises 4 bytes, the change sequence comprises 1 byte, the next fullbeacon time indication comprises 3 bytes, and the frame check comprises4 bytes.
 96. The apparatus of claim 94, wherein the source addresscomprises a basic service set identification (BSSID) of the accesspoint.
 97. The apparatus of claim 94, wherein the timestamp comprises ashortened timestamp comprising fewer bits than a full timestamp.
 98. Theapparatus of claim 97, wherein the timestamp comprises a one or moreleast significant bits of the full timestamp.
 99. The apparatus of claim94, further comprising: means for detecting a change in the changesequence; means for transmitting a probe request when a change in thechange sequence is detected; and means for receiving a probe response inresponse to the probe request.
 100. The apparatus of claim 94, whereinthe frame control field comprises a version field, a type field, asubtype field, a next full beacon time indication (NFBTI) present field,a service set identifier (SSID) present field, an internetworkingpresent field, a bandwidth field, a security field, and one or morereserved bits.
 101. The apparatus of claim 100, wherein the versionfield comprises 2 bits, the type field comprises 2 bits, the subtypefield comprises 4 bits, the NFBTI present field comprises 1 bit, theSSID present flag comprises 1 bit, the internetworking present fieldcomprises 1 bit, the bandwidth field comprises 3 bits, the securityfield comprises 1 bit, and the one or more reserved bits comprise 1 bit.102. The apparatus of claim 100, wherein type field comprises a value of“11” and the subtype field comprises a value of “0001,” indicating thatthe beacon is a compressed beacon.
 103. A non-transitorycomputer-readable medium comprising code that, when executed, causes anapparatus to: generate a compressed beacon comprising: a next fullbeacon time indication (NFBTI); and transmit the compressed beacon. 104.The medium of claim 103, wherein the next full beacon time indicationcomprises a time at which the access point will transmit a full beaconcomprising one or more fields not included in the compressed beacon.105. The medium of claim 104, wherein the next full beacon timeindication comprises the 3 most significant bytes, of the 4 leastsignificant bytes of a next target beacon transmit time (TBTT).
 106. Themedium of claim 103, wherein the next full beacon time indicationcomprises a flag indicating that the access point will transmit a fullbeacon comprising one or more fields not included in the compressedbeacon.
 107. The medium of claim 106, further comprising code that, whenexecuted, causes the apparatus to: generate the full beacon; andtransmit the full beacon.
 108. The medium of claim 103, wherein the nextfull beacon time indication comprises a value indicating a durationuntil the access point transmits the next full beacon.
 109. The mediumof claim 108, wherein the next full beacon time indication indicates thenumber of time units (TUs) until the access point transmits the nextfull beacon.
 110. The medium of claim 109, wherein the next full beacontime indication comprises a null value when number of beacon intervalsto the next full beacon is not determined.
 111. The medium of claim 103,wherein the compressed beacon comprises: a frame control field; a sourceaddress; a timestamp; a change sequence; the next full beacon timeindication; and a frame check.
 112. The medium of claim 111, wherein theframe control field comprises 2 bytes, the source address comprises 6bytes, the timestamp comprises 4 bytes, the change sequence comprises 1byte, the next full beacon time indication comprises 3 bytes, and theframe check comprises 4 bytes.
 113. The medium of claim 111, wherein thesource address comprises a basic service set identification (BSSID) ofthe access point.
 114. The medium of claim 111, wherein the timestampcomprises a shortened timestamp comprising fewer bits than a fulltimestamp.
 115. The medium of claim 114, wherein the timestamp comprisesa one or more least significant bits of the full timestamp.
 116. Themedium of claim 111, further comprising code that, when executed, causesthe apparatus to change the change sequence when an access point ornetwork configuration changes or when there is a substantial change inthe content of a full beacon.
 117. The medium of claim 111, wherein theframe control field comprises a version field, a type field, a subtypefield, a next full beacon time indication (NFBTI) present field, aservice set identifier (SSID) present field, an internetworking presentfield, a bandwidth field, a security field, and one or more reservedbits.
 118. The medium of claim 116, wherein the version field comprises2 bits, the type field comprises 2 bits, the subtype field comprises 4bits, the NFBTI present field comprises 1 bit, the SSID present flagcomprises 1 bit, the internetworking present field comprises 1 bit, thebandwidth field comprises 3 bits, the security field comprises 1 bit,and the one or more reserved bits comprise 1 bit.
 119. The medium ofclaim 116, wherein type field comprises a value of “11” and the subtypefield comprises a value of “0001,” indicating that the beacon is acompressed beacon.
 120. A non-transitory computer-readable mediumcomprising code that, when executed, causes an apparatus to: receive acompressed beacon comprising a next full beacon time indication (NFBTI);operate a wireless device in a first power mode for a duration based onthe next full beacon time indication; and transition the wireless deviceto a second power mode at the end of the duration, wherein the wirelessdevice consumes a first power when in the first power mode, and a secondpower when in the second power mode, the first power being lower thanthe second power.
 121. The medium of claim 120, wherein the next fullbeacon time indication comprises a time at which the access point willtransmit a full beacon comprising one or more fields not included in thecompressed beacon.
 122. The medium of claim 121, wherein the next fullbeacon time indication comprises the 3 most significant bytes, of the 4least significant bytes of a next target beacon transmit time (TBTT).123. The medium of claim 120, wherein the next full beacon timeindication comprises a flag indicating that the access point willtransmit a full beacon comprising one or more fields not included in thecompressed beacon.
 124. The medium of claim 123, further comprising codethat, when executed, causes the apparatus to receive the full beaconafter transitioning the wireless device to the second power mode. 125.The medium of claim 120, wherein the next full beacon time indicationcomprises a value indicating a duration until the access point transmitsthe next full beacon.
 126. The medium of claim 125, wherein the nextfull beacon time indication indicates the number of time units (TUs)until the access point transmits the next full beacon.
 127. The mediumof claim 127, wherein the next full beacon time indication comprises anull value when number of beacon intervals to the next full beacon isnot determined.
 128. The medium of claim 120, wherein the compressedbeacon comprises: a frame control field; a source address; a timestamp;a change sequence; the next full beacon time indication; and a framecheck.
 129. The medium of claim 128, wherein the frame control fieldcomprises 2 bytes, the source address comprises 6 bytes, the timestampcomprises 4 bytes, the change sequence comprises 1 byte, the next fullbeacon time indication comprises 3 bytes, and the frame check comprises4 bytes.
 130. The medium of claim 128, wherein the source addresscomprises a basic service set identification (BSSID) of the accesspoint.
 131. The medium of claim 128, wherein the timestamp comprises ashortened timestamp comprising fewer bits than a full timestamp. 132.The medium of claim 131, wherein the timestamp comprises a one or moreleast significant bits of the full timestamp.
 133. The medium of claim128, further comprising code that, when executed, causes the apparatusto: detect a change in the change sequence; transmit a probe requestwhen a change in the change sequence is detected; and receive a proberesponse in response to the probe request.
 134. The medium of claim 128,wherein the frame control field comprises a version field, a type field,a subtype field, a next full beacon time indication (NFBTI) presentfield, a service set identifier (SSID) present field, an internetworkingpresent field, a bandwidth field, a security field, and one or morereserved bits.
 135. The medium of claim 134, wherein the version fieldcomprises 2 bits, the type field comprises 2 bits, the subtype fieldcomprises 4 bits, the NFBTI present field comprises 1 bit, the SSIDpresent flag comprises 1 bit, the internetworking present fieldcomprises 1 bit, the bandwidth field comprises 3 bits, the securityfield comprises 1 bit, and the one or more reserved bits comprise 1 bit.136. The medium of claim 134, wherein type field comprises a value of“11” and the subtype field comprises a value of “0001,” indicating thatthe beacon is a compressed beacon.